'antonym' originates from 19th-century New Latin and Greek, specifically the word 'antōnymon', where 'anti-' meant 'against' and 'onoma' meant 'name'.

'antōnymon' (Greek) was adapted into New Latin as 'antonymum' and then borrowed into English in the 19th century as 'antonym'.

Initially, it meant 'a name opposite to another name', but over time it evolved into its current meaning of 'a word that means the opposite of another word'.