'anti-ejaculation' is formed from the prefix 'anti-' (from Greek anti, meaning 'against') combined with 'ejaculation' (from Latin roots for 'to throw out').

'ejaculation' comes from Latin 'eiaculatio' (from 'eiaculare' or related forms), passed into Medieval/Latin and Middle English as 'ejaculacion' and eventually became modern English 'ejaculation'; the modern compound 'anti-ejaculation' is formed in English by prefixing 'anti-' to that noun.

Originally 'ejaculation' had literal senses related to 'throwing out' and later acquired the sexual/physiological sense of 'expulsion (of semen)'; 'anti-ejaculation' therefore denotes opposition to or prevention of that action.