'anti-militarism' is formed from the prefix 'anti-' (from Greek 'anti' meaning 'against') combined with 'militarism' (the noun form built from 'military' + suffix '-ism').

'militarism' comes from French 'militarisme' and from Latin 'militaris' (relating to soldiers), itself from 'miles' meaning 'soldier'; the productive English prefix 'anti-' (from Greek 'antí') was attached in modern English to denote opposition, producing 'anti-militarism'.

Originally, 'militarism' referred to the influence or domination of military values or institutions; the compound 'anti-militarism' has consistently meant opposition to that influence or to military expansion, a sense that has remained stable into modern use.