'anti-vax' is a recent clipped compound formed from the prefix 'anti-' (meaning 'against') and 'vax', a short form of 'vaccine' or 'vaccination'; 'vaccine' ultimately comes from Latin 'vacca' ('cow') via French 'vaccin'.

'anti-' originates from Greek 'anti-' meaning 'against'; 'vax' is a 20th–21st century informal clipping of 'vaccine'/'vaccination' (English 'vaccine' from French 'vaccin', from Latin 'vacca' meaning 'cow'), and the compound 'anti-vax' emerged in contemporary English as a concise label for opposition to vaccines.

Initially formed simply as a short label meaning 'against vaccines', it has come to denote both an ideological position and social/political movement opposing vaccination and related policies.