Etymology
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annihilation (n.)

"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.

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annihilate (v.)
"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.
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