'antipoetically' originates from the Greek prefix 'anti-' (meaning 'against') combined with the adjective 'poetic' (from Latin 'poeticus', via Greek 'poietikos' from 'poietes' meaning 'maker' or 'poet').

'antipoetically' developed from the adjective 'antipoetic' / 'antipoetical' (anti- + poetic), where 'poetic' came into English via Latin 'poeticus' and Greek 'poietikos' (related to 'poietes'). Over time the adjective gained the adverbial suffix '-ally' to form the modern adverb.

Initially the components meant 'against' + 'poetic/poet' (i.e., opposed to poetry); over time the compound came to be used to describe actions or expressions done in an unpoetic or prosaic manner, which is its current sense.