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.
also moveable, late 14c., "disposed to movement;" c. 1400, "capable of being moved," from Old French movable, from moveir (see move (v.)). A moveable feast (early 15c.) is one in the Church calendar which, though always on the same day of the week, varies its date from year to year. Related: Movability.