'anti-atheism' originates from Greek and New Latin elements: specifically the prefix 'anti-' (Greek 'anti-') and 'atheism' (from Greek 'atheos' via Latin/French), where 'anti-' meant 'against' and 'atheos' meant 'without god'.

'atheos' (Greek) passed into Latin and then Old French as 'atheisme' and entered English as 'atheism'; the prefix 'anti-' (Greek) was attached to form the compound 'anti-atheism' in modern English.

Initially the components referred simply to being 'against' and to 'without god'; over time the compound came to mean specifically 'opposition to the doctrine or people identified as atheists'.