'anti-' originates from Greek, specifically the word 'ἀντί' (anti), where 'ἀντί' meant 'against'; 'national' originates from Latin, specifically the word 'natio', where 'natio' meant 'birth, people'.

'anti-national' is a compound formed by the Greek prefix 'anti-' plus the English adjective 'national' (which passed into English via Old French/Middle English from Latin 'natio'); the construction follows modern English compounding practices to mean 'against the nation'.

Initially, the elements together meant 'against the nation' in a literal sense; over time the term retained that core idea but has been applied more broadly to describe actions or opinions viewed as unpatriotic or hostile to a state's government or interests.