Origin and history of meddle

mid-14c., "action of blending," verbal noun from meddle (v.). Meaning "act or habit of interfering in matters not of one's proper concern" is from late 14c. As a present-participle adjective, from 1520s. Related: Meddlingly.

fourth letter of the Roman alphabet, from Greek delta, from Phoenician and Hebrew daleth, pausal form of deleth "door," so called from its shape.

The form of the modern letter is the Greek delta (Δ) with one angle rounded. As the sign for "500" in Roman numerals, it is said to be half of CIƆ, which was an early form of M, the sign for "1,000." 3-D for "three-dimensional" is attested from 1952.

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Unetymological -d- is the result of a tendency in English and neighboring languages, perhaps for euphony, to add -d- to -n-, and especially to insert or swap a -d- sound when -l- or -r- follow too closely an -n-.

Compare sound (n.1), thunder (n.), pound (v.), spindle, kindred, strand (n.2) "fiber of rope," dialectal rundel, rundle for runnel. Swound was a form of swoun (swoon) attested from mid-15c, and used by Malory, Spenser, Lyly, Middleton, Beaumont & Fletcher. Also obsolete round (n.) "whispering," variant of roun "secret, mystery, divine mystery" (from Old English run, source of rune), with unetymological -d attested by 15c. in the verb. 

Among the words from French are powder (n.), meddle, tender (adj.), remainder, gender (n.), also riband, jaundice. It is less evident in spider (an agent noun from the Germanic *spin- root), and perhaps explains lender in place of loaner.