'antiatheism' originates from Modern English, formed from the prefix 'anti-' and the noun 'atheism'; 'anti-' ultimately comes from Greek 'antí' meaning 'against', and 'atheism' ultimately comes from Greek 'atheos' meaning 'without god'.

'antiatheism' is a modern compound: 'anti-' (via Latin/French from Greek 'antí') was attached to 'atheism' (from Greek 'atheos' -> Late Latin 'atheismus' -> Old French 'athéisme' -> Middle English 'atheisme'), producing the modern English 'antiatheism'.

Initially formed to mean 'being against atheism', its meaning has remained essentially the same, referring to opposition to atheism or negative attitudes toward atheists.