'anti-unionist' originates from English compounds using the prefix 'anti-' (from Greek 'anti-' meaning 'against'), the noun 'union' (from Latin/French roots meaning 'joining' or 'unity'), and the agentive suffix '-ist' (from Greek/Latin suffixes meaning 'person who practices or supports').

'anti-' (Greek) + 'union' (via Old French/Latin 'unio' meaning 'unity') combined with the English agentive suffix '-ist' to form 'anti-union' + '-ist' in modern English; the compound arose in contexts of labor relations in the late 19th to 20th centuries as debates over unionization increased.

Initially formed to label persons or positions 'against unionization' in labor disputes; the core meaning has remained largely stable as referring to opposition to trade unions, though usage has varied in political and industrial contexts.