"reduce to nothing," 1520s, from Medieval Latin annihilatus, past participle of annihilare "reduce to nothing," from Latin ad "to" (see ad-) + nihil "nothing" (see nil). Related: Annihilated; annihilating.
Middle English had a past-participle adjective annichilate "destroyed, annulled, reduced to nothing" (late 14c.), from past participle of Old French anichiler "annihilate, destroy" (14c.) or the Medieval Latin verb.