'anti-Republican' originates from the Greek prefix 'anti-' and from the word 'Republican', which ultimately comes via Latin and French from Latin 'res publica'; 'anti-' meant 'against' and 'res publica' meant 'public affair'.

'anti-' (Greek) was combined with modern English 'Republican' (from Latin 'res publica' → Old French 'republique' → English 'republic' + adjectival suffix '-an') to form the compound 'anti-Republican' in modern political usage, particularly from the 19th–20th centuries onward.

Initially compounds with 'anti-' often signified general opposition ('against X'); 'anti-Republican' could originally mean 'against republican forms of government' but in modern political contexts it has come to be used chiefly to mean 'opposed to the Republican Party' (especially in the U.S.).