'anti-militarily' originates from English, specifically formed from the prefix 'anti-' and the adjective 'military'. The prefix 'anti-' comes from Greek 'anti' meaning 'against', and 'military' traces back through Old French to Latin 'militaris' (from 'miles' meaning 'soldier').

'military' came into English via Old French 'militaire' from Latin 'militaris' (related to 'miles', 'soldier'); the modern compound form 'anti-military' and its adverbial form 'anti-militarily' are created in English by adding the prefix 'anti-' and the adverbial suffix '-ly'.

Individually, 'military' originally meant 'relating to soldiers or soldiers' service'; with the addition of the prefix 'anti-' the compound's sense became 'opposed to military influence or the use of armed force', and the adverbial form means 'in that opposing manner'.