'counteractive' originates from English, specifically the word 'counteract' plus the adjectival suffix '-ive', where 'counter-' meant 'against' (from Old French/Latin) and 'act' meant 'to do' or 'act' (from Latin 'actus').

'counteractive' changed from the verb 'counteract' (formed in the 16th century from the prefix 'counter-' + 'act') by adding the suffix '-ive' to create an adjective meaning 'having the quality of counteracting'. 'Counter-' itself comes via Old French 'contre' from Latin 'contra', and 'act' comes from Latin 'actus' (from 'agere').

Initially the root meant 'to act against' (as in the verb 'counteract'), but over time the derived adjective 'counteractive' came to mean 'acting to oppose or reduce the effect' in a descriptive sense.