"act of reducing to non-existence," 1630s, from French annihilation (restored from Old French anichilacion, 14c.), or directly from Medieval Latin annihilationem (nominative annihilatio), noun of action from past-participle stem of annihilare "reduce to nothing" (see annihilate). In theology, an Annihilationist (1850) believed that the wicked were annihilated after death rather than sent to eternal suffering.
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.