'anti-ejaculatory' is a modern English compound formed by prefixing 'anti-' (from Greek 'anti', meaning 'against') to 'ejaculatory' (the adjectival form of 'ejaculate').

'ejaculate' comes from Latin roots (from ex-/e- 'out' + iaculare/—related to 'to throw'), passed into English as 'ejaculate' and then 'ejaculatory' as the adjective; 'anti-' (Greek) was later attached in modern English usage to form the compound 'anti-ejaculatory' in 20th-century medical/clinical contexts.

Originally 'ejaculate' had senses relating to 'throwing out' and later came to be used specifically for expulsion of semen; 'anti-ejaculatory' developed to describe agents, actions, or properties opposing that function.