discomfort n.

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).

late 13c., conforten "to cheer up, console, soothe when in grief or trouble," from Old French conforter "to comfort, to solace; to help, strengthen," from Late Latin confortare "to strengthen much" (used in Vulgate), from assimilated form of Latin com-, here perhaps an intensive prefix (see com-), + fortis "strong" (see fort).

The change of -n- to -m- began in English 14c. In Middle English also "give or add strength to" (c. 1300); "encourage, urge, exhort" (c. 1300). Related: Comforted; comforting.

c. 1200, discomfiten, "to undo in battle, defeat, overthrow," from Anglo-French descomfiter, Old French desconfire "to defeat, destroy," from des- "not" (see dis-) + confire "make, prepare, accomplish," from Latin conficere "to prepare," from com- "with" (see com-) + combining form of facere "to make, to do" (from PIE root *dhe- "to set, put").

General sense of "defeat or overthrow the plans or purposes of" is from late 14c. Weaker sense of "disconcert" is first recorded 1520s in English, probably by confusion with discomfort. Related: Discomfited; discomfiting.