Words related to des-
word-forming element of Latin origin meaning 1. "lack of, not" (as in dishonest); 2. "opposite of, do the opposite of" (as in disallow); 3. "apart, away" (as in discard), from Old French des- or directly from Latin dis- "apart, asunder, in a different direction, between," figuratively "not, un-," also "exceedingly, utterly." Assimilated as dif- before -f- and to di- before most voiced consonants.
The Latin prefix is from PIE *dis- "apart, asunder" (source also of Old English te-, Old Saxon ti-, Old High German ze-, German zer-). The PIE root is a secondary form of *dwis- and thus is related to Latin bis "twice" (originally *dvis) and to duo, on notion of "two ways, in twain" (hence "apart, asunder").
In classical Latin, dis- paralleled de- and had much the same meaning, but in Late Latin dis- came to be the favored form and this passed into Old French as des-, the form used for compound words formed in Old French, where it increasingly had a privative sense ("not"). In English, many of these words eventually were altered back to dis-, while in French many have been altered back to de-. The usual confusion prevails.
As a living prefix in English, it reverses or negatives what it is affixed to. Sometimes, as in Italian, it is reduced to s- (as in spend, splay, sport, sdain for disdain, and the surnames Spencer and Spence).
c. 1400, deschaunt, "a counterpoint added to a given melody," from Anglo-French deschaunt, Old French deschant, from Medieval Latin discantus "refrain, part-song," from Latin dis- "asunder, apart" (see dis-) + cantus "song, a singing; bird-song," from past participle stem of canere "to sing" (from PIE root *kan- "to sing").
The English spelling was partly Latinized in 16c., but it is an exception for its retention of des- in English. It is attested from 1560s in the sense of "the art of composing part-music," also "the upper part or voice." It is attested from 1570s as "a warbled song, a song with various modulations." The transferred sense of "a continued discourse or series of comments on a subject" is recorded from 1590s.
A metaphor taken from musick, where a simple air is made the subject of a composition, and a number of ornamented variations composed upon it. [Hensleigh Wedgwood, "A Dictionary of English Etymology," 1859]