'anti-militarist' originates from modern English, composed of the prefix 'anti-' (from Greek 'antí', meaning 'against') and 'militarist' (formed from 'military', ultimately from Latin 'militaris' meaning 'of soldiers', plus the agent suffix '-ist').

'military' derives from Latin 'militaris' ('of soldiers'); it entered English via Old French/Latin forms as 'military'. 'Militarism' arose in the 19th century to describe political dominance of the military, and 'militarist' became the agent noun. The compound 'anti-militarist' developed in modern English by adding the prefix 'anti-' to oppose that idea.

Initially related elements meant 'of soldiers' (Latin 'militaris'); 'militarism' later came to mean political or social dominance of military values, and 'anti-militarist' evolved to mean someone or something opposing that dominance.