If the original writing in Revelation 3:14 was in Koine Greek, why would a word need to be transliterated from Hebrew?

John, the human author of the book of Revelation, frequently used words borrowed directly from the Hebrew. Here is a sample:

• "Amen" in Rev 1:6, 7, 3:14, 5:15, 7:12, 19:4, 22:20.
• "Abaddon" in Rev 9:11
• "harmageddon" in Rev 16:16
• "paradise" (a persian word) in Rev 2:7

This is also typical of the rest of the NT:

• "Golgotha" in John 19:17
• "Gabbatha" in John 19:13
• "rabboni" in John 20:16
• "Bethesda" in John 5:2
• "Melchizedek" in Heb 5:10, 7:1, 10, 15, 17, etc
• "Arimathea" in Matt 27:57, mark 15:43, Luke 23:51, John 19:38.
• "Jesus" is the Greek equivalent of יְהוֹשׁוּעַ (Yehoshua)
• many other people's names such as Mary, Joseph, Simon, John, etc, etc.
• etc, etc

In a place where several languages (Aramaic, Hebrew, Greek Latin) lived side by side, it is entirely expected that they would "infect" one another.

Therefore, it should not surprise us to find Latin words in the NT as well such as:

• "assarion", in Matt 10:29, Luke 12:6
• "Denarius"
• "centurion"
• "quadrans" in Mark 12:42
• "census"
• etc, etc
• Many people's names such as Paulus, Titus,

People speaking or writing in one language frequently borrow words from other languages. I believe the French have adopted "le five-o'clock" to denote an afternoon light meal. The implication is that the Hebrew word "Amen" has been borrowed in the same way by the Greek-speaking church.

Revelation 3:14 presents Jesus Christ as “the Amen, the faithful and true witness, the beginning of the creation of God.” The deliberate use of the untranslated Hebrew term אָמֵן (ʾāmēn), rendered in Greek as ὁ ἀμήν, constitutes a profound Christological claim. By applying to the exalted Christ a divine title drawn directly from Isaiah 65:16—where God is twice called אֱלֹהֵי אָמֵן (“the God of Amen”)—the Apocalypse identifies Jesus with none other than Yahweh himself. This identification, far from being incidental, forms part of a sustained pattern in which New Testament authors apply Old Testament Yahweh-texts to Jesus, thereby affirming his full deity within the one being of God. The present essay examines the linguistic, exegetical, and theological significance of this title, demonstrating that the retention of the Hebrew form אָמֵן in a Greek composition is not an anomaly but a deliberate theological signal of Jesus’ consubstantiality with the Father.

I. The Linguistic Anomaly as Theological Intentionality

The question naturally arises: if Revelation was composed in Koine Greek, why does the speaker introduce himself with the Hebrew word אָמֵן rather than its standard Greek equivalents (e.g., ναί, ἀληθῶς, or γένοιτο)? The answer lies not in linguistic necessity but in theological precision.

In Isaiah 65:16, the Masoretic Text reads אֱלֹהֵי אָמֵן—literally “the God of Amen.” The Septuagint renders this as ὁ θεὸς ὁ ἀληθινός (“the true God”), accurately capturing the semantic force of אָמֵן as “truth, faithfulness, certainty.” Yet when the risen Christ speaks in Revelation 3:14, John does not follow the LXX’s translational choice. Instead, he retains the Hebrew term in its transliterated form: ὁ ἀμήν.

This is not mere Semitic flavor. Throughout Revelation, Hebrew and Aramaic terms are occasionally preserved for emphatic theological effect: ἀββα (14:6), Ἁλληλουϊά (19:1, 3, 4, 6), and especially the divine name in its cryptic form Ἀλφα καὶ τὸ Ὦ (1:8; 21:6; 22:13). The retention of אָמֵן belongs to this same category of sacred onomastic markers. By refusing to translate the word, John forces the reader to hear the exact divine title from Isaiah 65:16 applied now to Jesus. The effect is unmistakable: the one who speaks from the throne is none other than אֱלֹהֵי אָמֵן himself.

II. The Old Testament Background: Isaiah 65:16 and the God of Amen

Isaiah 65:16 forms part of the great new-creation oracle (Isa 65:17–25) in which Yahweh promises to create new heavens and a new earth. Twice in a single verse he is called אֱלֹהֵי אָמֵן:

“That he who blesses himself in the earth shall bless himself in the God of Amen [בֵּאלֹהֵי אָמֵן], and he that swears in the earth shall swear by the God of Amen.”

The expression is unique in the Hebrew Bible. The noun אָמֵן derives from the root אמן (“to confirm, support, be faithful”), and in its nominal form functions as a divine title emphasizing absolute reliability and truthfulness (cf. the rabbinic designation קוּשְׁטָא חִיָּיא, “the living Truth,” applied to God). The double occurrence in Isaiah 65:16 is therefore highly significant: Yahweh himself is the ultimate ground of all truth and faithfulness.

When the Septuagint translators rendered this as ὁ θεὸς ὁ ἀληθינός, they correctly conveyed the meaning. But by the first century, Jewish interpreters were increasingly sensitive to the danger of pronouncing the divine name. The preservation of אָמֵן in its Hebrew form thus served a dual purpose: it avoided translation that might dilute the title’s uniqueness while simultaneously evoking the full weight of the Isaiah text.

III. The Christological Appropriation in Revelation 3:14

John’s use of ὁ ἀμήν in Revelation 3:14 is therefore a calculated act of identification. The speaker does not say “I am the true one” (ὁ ἀληθινός)—though he will use that very title of himself in v. 7—but “I am the Amen.” The definite article is crucial: Jesus is not a faithful witness; he is the Amen—the ultimate embodiment of the divine attribute that Isaiah ascribes to Yahweh alone.

This pattern of applying Yahweh-texts to Jesus is pervasive in the New Testament generally and in Revelation particularly:

• Isaiah 44:6 / Revelation 1:17; 2:8; 22:13 (“the First and the Last”)
• Isaiah 41:4; 48:12 / Revelation 1:8; 21:6 (“who is and who was and who is to come”)
• Isaiah 45:23 / Philippians 2:10–11; Revelation 5:13 (every knee bows)

In each case, titles or actions reserved for Yahweh in the Old Testament are transferred without qualification to Jesus. The use of ὁ ἀμήν belongs precisely to this category of explicit divine-name transference.

IV. The Trinitarian Implication

The theological force of this identification is decisive for Trinitarian Christology. When Jesus calls himself ὁ ἀμήν, he is not merely claiming to speak truly; he is claiming to be the personal embodiment of the divine faithfulness that Isaiah ascribes to Yahweh. The one who sits on the throne and the Lamb are simultaneously distinguished and identified (Rev 5:13; 7:10; 22:1, 3). The Amen who speaks to Laodicea is the same divine person who spoke to Isaiah—now incarnate, crucified, risen, and enthroned.

To object that a Greek composition should not preserve Hebrew terms is to miss the point entirely. The preservation is the point. John could easily have written ὁ ἀληθινός (as in Rev 3:7). Instead, he forces the reader to hear the Hebrew divine title and recognize that the risen Jesus is now the bearer of that title. This is not Semitic coloration; it is a Christological confession of the highest order.

Conclusion

The presence of the untranslated אָמֵן in Revelation 3:14 is neither accidental nor merely stylistic. It is a deliberate theological signal that the one speaking from the throne is Yahweh himself in the person of the exalted Son. The Laodicean letter thus opens with a thunderous affirmation of the deity of Christ: the Amen, the faithful and true witness, the ἀρχή of the creation of God—is none other than אֱלֹהֵי אָמֵן, the God of the Amen, the faithful God of Israel.

In an age that prided itself on philosophical sophistication, John refuses to accommodate. He will not dilute the scandal of the incarnation by translating away the divine name. He will not allow the church to forget that the one who knocks at the door of Laodicea (3:20) is the same one who spoke from Sinai and promised new creation in Isaiah 65. He is the Amen—the eternal Word who was with God and was God, now forever enthroned as the Lamb who was slain.

The Laodiceans are neither cold nor hot. But the one who addresses them is the Amen—the final, unchangeable, utterly reliable Word of God himself. And he stands at the door and knocks.

He is not a creature.
He is the Creator who has become flesh—the faithful God in person—calling his church to himself.

That is the force of the Hebrew word that John refused to translate.
That is the gospel according to the Apocalypse.

Stephen is correct. I'll give you another example: Bohairic Coptic frequently transliterates the Greek word, monogenes, using Coptic characters (ⲘⲞⲚⲞⲄⲈⲚⲎ) and that is largely because there is not a word in the Bohairic language that carries the same significance.

But a question I think is worth asking: Why do you think Rev. 3:14 was written in Hebrew? Why could it not be the case that a Greek writer who was familiar with the Greek OT (the LXX) was alluding to a passage found in the Greek OT (i.e., Isaiah 65:16), which uses the same word? What is it specifically about the usage in Rev. 3:14 that makes it so special?

Would it not be easier to say that the term found in Isaiah was transliterated into Greek by a native Jew, and an author sometime later (whether they be Jew or not), picked up on the language used in Isaiah 65 LXX?

Surely, we cannot say that everytime we stumble across the word, ἀμήν, that the author whose letter contains it, was originally writing in Hebrew.

Revelation deliberately uses specifically hebrew and greek words either in isolation or combination in order to illustrate particularly hebrew and greek applications.

For instance :

... the fourth seal ...

I looked, and there before me was a pale horse! Its rider was named Death, and Hades was following close behind him. They were given power over a fourth of the earth to kill by sword (ῥομφαία), famine and plague, and by the wild beasts of the earth.

Revelation 6:7,8 NIV

In this instance, the fourth seal, beginning under Maximinus Thrax (235-238), "Maximinus the Thracian", was marked by a period of famine and plague but also by two varieties of conflict, civil war, and barbarian predations.
Death, here θάνατος, a generic greek term, is coupled with ῥομφαία, and not the "dagger" or μάχαιρα of the second seal. A weapon not of assassination but of war, notably the Thracian sword.
Concomitant to these civil wars, the empire for the first time was tested by successive barbarian invasions, often following the internal strife. This attack by "the wild beasts of the earth" given the more specifically greek label ᾅδης, the barbarians being the outsiders to the Romans.

And the fifth angel blew his trumpet ...

... a star fallen from heaven to earth ... he opened the shaft of the bottomless pit (ἄβυσσος) ...

They have as king over them the angel of the bottomless pit (ἄβυσσος); his name in Hebrew is Abad′don, and (or then, also καὶ) in Greek he is called Apol′lyon.

Revelation 9:1,1,2,11 RSV

Muhammad, the star that fell on the empire, first taking control of the Arabian world, and then moving through the Levant, or the shaft which grants access to the "bottomless pit" - more correctly the "depths of the sea", the sea being the Mediterranean out of which the beast appears, appropriately signified by firstly, the hebrew term Ἀβαδδών, and then secondly, the greek term Ἀπολλύων.

Then they gathered the kings together to the place that in Hebrew is called Armageddon.

Revelation 16:16 NIV

This prophecy variously described in the hebrew scriptures and employing the figure of sheaves of gathered wheat (עָמַר aw-mar') in a valley (גַּיְא gah'-ee) for threshing or judgement (דִּין deen) - or in greek ΑΡΜΑΓΕΔΩΝ - Armageddon (Daniel 2:35, Micah 4:11-13, Joel 3:1-2, Joel 3:12-14, Zechariah 14:2-4, et cetera).

I saw the dead, great and small ...

The sea gave up the dead that were in it, and death and Hades gave up the dead that were in them ...

Then death and Hades were thrown into the lake of fire.

... there was no longer any sea.

Revelation 20:12,13,14; Revelation 21:1 NIV

At the second death, and the concomitant second resurrection and judgement, there will be three classes of people, that live and die, until that time, that have no part in the first resurrection.
Those of the nations between the flood and the arrival of messiah, other than the natural olive tree, termed by the scripture as "the sea" (Isaiah 17:12), those between messiah and the millennial kingdom, other than the wild olive tree, represented appropriately by the greek or gentile term "Hades", and those during the millenial kingdom, employing the remaining general term, "death" or θάνατος. All these no longer existing in the perfected new order, with the new heavens, and the new earth.

Fulfillment of Psalms 88 and 89.

Jesus Christ, who is the faithful witness, the firstborn from the dead, and the ruler of the kings of the earth.

Revelation 1:5 NIV

These are the words of the Amen, the faithful and true witness, the ruler of God’s creation.

Revelation 3:14 NIV

I saw heaven standing open and there before me was a white horse, whose rider is called Faithful and True.

Revelation 19:11 NIV

While it doesn't seem at all sensible to limit Jesus, especially after his resurrection to life, to a verbatim recitation of the hebrew bible, this thrice employed description is clearly intended to take the reader back to Psalms 88 and 89, to the death and resurrection, and the promises of an everlasting throne.

"Once for all, I have sworn by my holiness—
and I will not lie to David—
that his line will continue forever
and his throne endure before me like the sun;
it will be established forever like the moon,
the faithful¹ witness² in the sky."

Praise be to the Lord forever!
Amen and Amen.

Psalm 89:35-37,52 NIV
¹ LXX : πιστός
² LXX : μάρτυς

Psalm 88 and 89 form a pair :

A song. A psalm of the Sons of Korah. For the director of music. According to mahalath leannoth¹. A maskil of Heman the Ezrahite.

Psalm 88
¹ NIV : "The Suffering of Affliction"

A maskil of Ethan the Ezrahite.

Psalm 89

Heman ("faithful"), and Ethan ("everlasting"), are brothers, employed in the court of David, and singled out for their wisdom under Solomon, who collectively walk us through the death and resurrection of messiah, in Psalm 88 (in the spirit of "My God, my God, why have you forsaken me?"), and the millennial kingdom and beyond, in Psalm 89 :

The sons of Zerah:
Zimri, Ethan, Heman, Kalkol and Darda—five in all.

God gave Solomon wisdom ...
He was wiser than anyone else, including Ethan the Ezrahite—wiser than Heman, Kalkol and Darda, the sons of Mahol.

1 Chronicles 2:6; 1 Kings 4:29,31 NIV

Psalm 89, until verse 37, where the particular phrase "faithful witness" occurs, concerns itself with the majesty of the creation, promises to David, and the establishing of an everlasting throne. However after verse 37, there's a lamentation by the author, regarding the difficulty in waiting in expectation for the everlasting throne.
In other words, there's a progression, seen in the two Psalms, of the "faithful witness", through death and the resurrection, through a throne over the kings of the earth and creation, these circumstances paralleled by the first two occurrences in Revelation, with the final portion of the second Psalm finding fulfillment in the final statement by Jesus in Revelation.

The death and resurrection of Psalm 88 paralleled by the faithful witness :

Jesus Christ, who is the faithful witness, the firstborn from the dead, and the ruler of the kings of the earth.

Revelation 1:5 NIV

The throne ruling over the creation paralleling Psalm 89 till verse 37, Jesus being not only a faithful witness in life and death, but also being found true (ἀληθινός - the genuine or true one, but primarily "not concealed") :

These are the words of the Amen, the faithful and true witness, the ruler of God’s creation.

Revelation 3:14 NIV

The expectant lamentation after verse 37 of Psalm 89 fulfilled in the "new name", Jesus no longer being a witness, as all have the knowledge of god, from the smallest to the greatest :

I saw heaven standing open and there before me was a white horse, whose rider is called Faithful and True.

Revelation 19:11 NIV

It seems reasonable that just as Jesus walks through the Psalms, that the unique occurrence of amen is designed to emphasize his fulfillment of the promises to David in the transition from faithful witness, to faithful and revealed (or true).

Praise be to the Lord forever!
Amen and Amen.

Psalm 89:52 NIV

Isaiah 65
Here is the passage noted by the OP in context:

¹⁵ You shall leave your name to my chosen for a curse, and the LORD God will put you to death, but his servants he will call by another name, ¹⁶ so that he who blesses himself in the land shall bless himself by the God of truth, and he who takes an oath in the land shall swear by the God of truth; because the former troubles are forgotten and are hidden from my eyes. ¹⁷ “For behold, I create new heavens and a new earth, and the former things shall not be remembered or come into mind. (Isaiah 65 ESV)

The Hebrew text for Isaiah 65:16 is

אשׁר המּתבּרך בּארץ יתבּרך בּאלהי אמן והנּשׁבּע בּארץ ישּׁבע בּאלהי אמן כּי נשׁכּחוּ הצּרות הראשׁנות וכי נסתּרוּ מעיני

...the God of Truth is בּאלהי אמן, literally in God Amen. אמן, 'āmēn means truly or so be it. It is used 12 times in Deuteronomy 27:15-26 always as the people's response to a specific curse for breaking the law. Essentially it is an expression of affirmation.

We should note Isaiah speaks of a curse and a blessing which recalls the main use of the Hebrew. A few translations understand the passage in that light:

Those who pronounce a blessing in the land will do so by the God called Amen; those who make a solemn pledge in the land will do so by the God called Amen. Past troubles will be forgotten and hidden from my sight. (CEB, also AMPC, DRA, EHV, OJB)

The Wycliffe and Douay-Rheims (from the Vulgate) go so far as to treat אמן as it is used everywhere else, and translate the words literally:

In which he that is blessed on earth, shall be blessed in God, amen; and he that sweareth in (the) earth, shall swear in God faithfully (In which he who is blessed in the land, shall be blessed by God, amen; and he who sweareth in the land, shall swear faithfully by God); for the former anguishes be given to forgetting, and for those be hid from your eyes. (WYC)
In which he that is blessed upon the earth, shall be blessed in God, amen: and he that sweareth in the earth, shall swear by God, amen: because the former distresses are forgotten, and because they are hid from my eyes. (DRA)

The Old Testament for the Churches of Asia was the Septuagint. Here is the passage in Greek:

¹⁵ For you shall leave your name for fullness to my chosen one, but the Lord will do away with you. But to those who are subject to him, a new name shall be called, ¹⁶ which shall be blessed on the earth; for they shall bless the true God, and those who swear on the earth shall swear by the true God, for they shall forget their first affliction, and it shall not come up into their heart. ¹⁷ For heaven will be new, and the earth will be new, and they shall not remember the former things, nor shall they come upon their heart, ¹⁸ but they shall find joy and gladness in it, because look, I am making Ierousalem as gladness, and my people as a joy. (LXX-Isaiah 65 NETS)

The LXX did not transliterate אמן. Translators opted to interpret בּאלהי אמן as τὸν θεὸν τὸν ἀληθινόν, the God of the truth. Based on the LXX, אמן in this instance would be understood as truth.

Isaiah 65-66
Benjamin D. Sommer gives this synopsis of the final two chapters of Isaiah:

65.1-66.24: Blessing and Doom Earlier Deutero-Isaiah alluded to a distinction between faithful and sinful Judeans, intimating that the final act of salvation will benefit only the former; see 57.19-21, 59.1-21, and passages which contrast the ideal servant nation and the blind servant, such as 42.1-9, and 42.18-43. Here the prophet sharpens this distinction. The nation includes both those who patiently wait for the LORD's salvation and those who have taken up the worship of other deities in addition to or in place of the true God. The latter will suffer the sort of punishment often associated in the Bible with Assyrians, Babylonians, and Edomites. Conversely, the righteous from other nations will enjoy the privilege of worshipping at Zion.

65.1-16: The faithful and the apostates within Israel. The opening verses set up the contrast at the heart of this unit by describing the behavior and fate of each group. ¹

With respect to Revelation there parallels taken from Isaiah's final two chapters: true and false worship, faithful and unfaithful people, faithful servants receiving a new name, new heaven and new earth, complete victory and destruction of all who oppose God. Conceptually what Jesus has done is to make allusion to the final chapters of Isaiah in the final letter to the seven churches. This allusion is strengthened by transliterating the Hebrew אמן.

Revelation

“To the messenger of the church in Laodicea, write: ‘The Amen, the witness who is faithful and true, the originator of God’s creation, says this: (Revelation 3:14 ISV)

The dependence is on both the Hebrew אמן, transliterated as ἀμήν and the Greek τὸν ἀληθινόν. ἀμήν preserves the Hebrew אמן (which the LXX interpreted). Prefacing this with the article, ὁ ἀμήν treats the term as a title with respect to Isaiah 65:16, Jesus replaced God with the Truth, and then adds ὁ πιστὸς to τὸν ἀληθινόν, creating the hendiadys, ὁ πιστὸς καὶ ἀληθινόν.

LXX-Isaiah 65:16 - τὸν θεὸν, τὸν ἀληθινόν
Revelation 3:14 - ὁ ἀμήν, ὁ πιστὸς καὶ ἀληθινόν

Isaiah 65:17 continues speaking of a new heaven and a new earth, another theme in Revelation. Here it illuminates the meaning of ἡ ἀρχὴ which follows ἀληθινός. The ISV (and others) understand ἡ ἀρχὴ as originator. So the Amen, the witness who is faithful and true, the originator of God’s creation... He is the originator of a new heaven and a new earth (Isaiah 65:17).

The reference to Isaiah 65:17 is made explicit near the end of Revelation:

Then I saw a new heaven and a new earth, for the first heaven and the first earth had passed away, and the sea was no more. (Revelation 21:1)

1. Benjamin D. Sommer, The Jewish Study Bible, Edited by Adele Berlin and Marc Zvi Brettler, Oxford University Press, 2004, p. 911.