1530s "unfavorable regard, slight displeasure;" 1580s, "state of being regarded unfavorably;" see dis- "the opposite of" + favor (n.). As a verb, "withdraw or withhold favor or support," from 1560s. Related: Disfavored; disfavoring.
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. 1300, "attractiveness, beauty, charm" (archaic), from Old French favor "a favor; approval, praise; applause; partiality" (13c., Modern French faveur), from Latin favorem (nominative favor) "good will, inclination, partiality, support," coined by Cicero from stem of favere "to show kindness to," from PIE *ghow-e- "to honor, revere, worship" (cognate: Old Norse ga "to heed").
Meaning "good will, kind regard" is from mid-14c. in English; sense of "act of kindness, a kindness done" is from late 14c. Meaning "bias, partiality" is from late 14c. Meaning "thing given as a mark of favor" is from late 15c. Phrase in favor of recorded from 1560s.