'annihilate' originates from Latin, specifically the word 'annihilare,' where 'ad-' meant 'to/toward' (which assimilated to 'an-') and 'nihil' meant 'nothing'.

'annihilare' passed through Late Latin and entered English via Middle French/Medieval Latin forms (e.g. Middle French 'annihiler' / Medieval Latin 'annihilare'), eventually becoming the modern English word 'annihilate'.

Initially it meant 'to reduce to nothing' (literally 'make into nothing'), and over time it has retained that core sense while also extending metaphorically to 'defeat utterly' or 'render irrelevant'.