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.

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), gender (n.), thunder (n.), 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. Among the words from French are powder (n.), meddle, tender (adj.), remainder, 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.

early 14c., riban, ribane, from Anglo-French rubain, Old French riban "a ribbon," variant of ruban (13c.), a word of unknown origin, possibly from a Germanic compound whose second element is related to band (n.1); compare Middle Dutch ringhband "necklace."

The modern spelling is from mid-16c. Originally a stripe in a material; the sense of "narrow woven band of some find material" for ornamental or other purposes is by 1520s. The word was extended to other long, thin, flexible strips by 1763; the meaning "ink-soaked strip wound on a spool for use on a typewriter" is by 1883. A a torn strip of anything (fabric, clouds, etc.) by 1820. As a verb, "adorn with ribbons," by 1716. Related: Ribboned. The custom of wearing colored ribbon loops on the lapel to declare support for some group perceived as suffering or oppressed began in 1991 with AIDS red ribbons.