disappoint v.

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 14c., "to decide, resolve; to arrange the time of (a meeting, etc.)," from Anglo-French appointer, Old French apointier "make ready, arrange, settle, place" (12c., Modern French appointer), from apointer "duly, fitly," from phrase à point "to the point," from a- "to" (see ad-) + point "point," from Latin punctum "small hole made by pricking" (from nasalized form of PIE root *peuk- "to prick").

The etymological sense is "to come to a point" (about some matter), therefore "agree, settle." The meaning "put in charge, authoritatively nominate or assign" is early 15c. Related: Appointed; appointing.