Origin and history of to-be

Old English beon, beom, bion "be, exist, come to be, become, happen," from Proto-Germanic *biju- "I am, I will be." This "b-root" is from PIE root *bheue- "to be, exist, grow," and in addition to the words in English it yielded the German present first and second person singular (bin, bist, from Old High German bim "I am," bist "thou art"), the Latin perfective tenses of esse (fui "I was," etc.), Old Church Slavonic byti "be," Greek phu- "become," Old Irish bi'u "I am," Lithuanian būti "to be," Russian byt' "to be," etc.

The modern verb to be in its entirety represents the merger of two once-distinct verbs, the "b-root" represented by be and the am/was verb, which was itself a conglomerate. Roger Lass ("Old English") describes the verb as "a collection of semantically related paradigm fragments," while Weekley calls it "an accidental conglomeration from the different Old English dial[ect]s." It is the most irregular verb in Modern English and the most common.

Collective in all Germanic languages, it has eight different forms in Modern English: BE (infinitive, subjunctive, imperative); AM (present 1st person singular); ARE (present 2nd person singular and all plural); IS (present 3rd person singular); WAS (past 1st and 3rd persons singular); WERE (past 2nd person singular, all plural; subjunctive); BEING (progressive & present participle; gerund); BEEN (perfect participle).

The paradigm in Old English was: eom, beo (present 1st person singular); eart, bist (present 2nd person singular); is, bið (present 3rd person singular); sind, sindon, beoð (present plural in all persons); wæs (past 1st and 3rd person singular); wære (past 2nd person singular); wæron (past plural in all persons); wære (singular subjunctive preterit); wæren (plural subjunctive preterit).

The "b-root" had no past tense in Old English, but often served as future tense of am/was. In 13c. it took the place of the infinitive, participle and imperative forms of am/was. Later its plural forms (we beth, ye ben, they be) became standard in Middle English and it made inroads into the singular (I be, thou beest, he beth), but forms of are claimed this turf in the 1500s and replaced be in the plural. For the origin and evolution of the am/was branches of this tangle, see am and was.

That but this blow Might be the be all, and the end all. ["Macbeth" I.vii.5]

Old English to, ta, te, "in the direction of, as far as (a place, state, goal)," opposite of from; also "for the purpose of, furthermore;" from West Germanic *to (source also of Old Saxon and Old Frisian to, Dutch toe, Old High German zuo, German zu "to"). Not found in Scandinavian, where the equivalent of till (prep.) is used.

This is reconstructed to be from PIE pronominal base *do- "to, toward, upward" (source also of Latin donec "as long as," Old Church Slavonic do "as far as, to," Greek suffix -dē "to, toward," Old Irish do, Lithuanian da-), from demonstrative *de-. Also see too.

English to also supplies the place of the dative in other languages. The near-universal use of to as the verbal particle with infinitives (to sleep, to dream, etc.) arose in Middle English out of the Old English dative use of to and helped shade out the Old English inflectional endings. In this use to is a mere sign, without meaning. Compare similar use of German zu, French à, de.

As an adverb of motion, direction, etc., "to a place in view, to a thing to be done," in Old English. This use was frequent in Middle English in verbal combinations where it renders Latin ad-, com-, con-, ex-, in-, ob-. As a conjunction, "until, up to the time that," by late Old English.

The distribution of verbs among at, to, with, of has been idiosyncratic and varied. Before vowels it was sometimes shortened to t'. The phrase what's it to you "how does that concern you?" (1819) is a modern form of an old question:

Huæd is ðec ðæs?

[John xxi:22, in Lindisfarne Gospel, c.950]

Used absolutely at the end of a clause. with ellipsis of infinitive (same as the proceeding clause: would do it but don't have time to), it is attested from 14c.; OED reports it "rare before 19th c.; now a frequent colloquialism."