'antimonarchally' originates from Modern English, specifically formed from the prefix 'anti-' (from Greek 'anti' meaning 'against'), the word 'monarch' (via Latin/Old French from Greek 'monarchos' meaning 'sole ruler'), and the adverbial suffix '-ally' (from adjective suffix '-al' + adverbial '-ly').

'antimonarchally' developed from the adjective 'antimonarchal' (a Modern English formation) which itself was built on 'monarch' (from Old French 'monarque' and Latin/Greek roots). The suffixes '-al' and '-ly' were added in sequence to form the adverb.

Initially the components meant 'against' + 'sole ruler'; the combined modern sense has remained 'opposed to monarchy' and is expressed in adjectival and adverbial forms.