incognito adj./adv.

word-forming element meaning "not, opposite of, without" (also im-, il-, ir- by assimilation of -n- with following consonant, a tendency which began in later Latin), from Latin in- "not," cognate with Greek an-, Old English un-, all from PIE root *ne- "not."

In Old French and Middle English often en-, but most of these forms have not survived in Modern English, and the few that do (enemy, for instance) no longer are felt as negative. The rule of thumb in English has been to use in- with obviously Latin elements, un- with native or nativized ones.

mid-14c., conisance, "device or mark by which something or someone is known," from Anglo-French conysance "recognition," later, "knowledge," from Old French conoissance "acquaintance, recognition; knowledge, wisdom" (Modern French connaissance), from past participle of conoistre "to know," from Latin cognoscere "to get to know, recognize," from assimilated form of com "together" (see co-) + gnoscere "to know" (from PIE root *gno- "to know").

Meaning "knowledge by observation or notice, understanding, information" is from c. 1400. In law, "the exercise of jurisdiction, the right to try a case" (mid-15c.). Meaning "acknowledgment, admission" is from 1560s. The -g- was restored in English spelling 15c. and has gradually affected the pronunciation, which was always "con-." The old pronunciation lingered longest in legal use.