disqualify 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).

mid-15c., qualifien, transitive, "to invest with (a quality), impart a certain quality to," from French qualifier (15c.) and directly from Medieval Latin qualificare "attribute a quality to; make of a certain quality," from Latin qualis "of what sort?," correlative pronominal adjective (see quality) + combining form of facere "to make" (from PIE root *dhe- "to set, put").

Meaning "to limit, modify by a limitation or reservation, restrict" is from 1530s, as is the sense of "to have or have taken the necessary steps for rendering oneself capable of holding an office, etc." The sense of "to be or become fit for an employment, office, etc." is by 1580s. Related: Qualified; qualifying.

1710s, "that which disqualifies;" 1770, "act of disqualifying; state of being disqualified;" noun of action or state from disqualify.