'antimonarchal' is formed from the prefix 'anti-' (from Greek) + 'monarchal' (from 'monarch' + adjectival suffix), where 'anti-' meant 'against' and 'monarch' ultimately comes from Greek 'monárkhēs' meaning 'sole ruler'.

'antimonarchal' developed in modern English by combining the productive prefix 'anti-' with the adjective 'monarchal' (itself from 'monarch' via Middle English and Old French), creating a term meaning 'against monarchy'.

Initially coined to denote opposition to a specific monarch or monarchy as an institution, its meaning has stayed largely the same: 'opposed to monarchy' or 'against monarchic rule'.