'antimonarchic' originates from Greek elements, specifically the prefix 'anti-' from Greek 'ἀντί' meaning 'against' and 'monarchic' from Greek 'μονάρχης' (via Latin/Old French), where 'μόνος' meant 'single' and 'ἄρχων' meant 'ruler'.

'antimonarchic' developed as a compound of 'anti-' + medieval/modern formations of 'monarchic' (Medieval Latin 'antimonarchicus' or analogous constructions), and eventually entered modern English as 'antimonarchic'.

Initially it carried the literal sense 'against single-ruler rule' (against a 'monarch'), and over time it has been used in English to mean broadly 'opposed to monarchy' or 'opposed to the institution of monarchy'.