'anti' originates from Greek, specifically the word 'antí' (ἀντί), where 'anti-' meant 'against' or 'opposite'.

'anti' entered English via Latin and French as the combining form 'anti-' and was used in compounds (e.g., anti-clerical). It has remained productive as a prefix and also developed informal standalone uses (noun/adjective).

Initially it meant 'against' or 'opposite' in Ancient Greek, and this core meaning has largely remained the same, though its use expanded into a productive English prefix and informal standalone word.