'anti-medievally' originates from modern English, specifically the prefix 'anti-' (from Greek 'ἀντί' meaning 'against') + 'medieval' (from Medieval Latin 'medium aevum' meaning 'middle age') with the adverbial suffix '-ly' (from Old English '-lic'/'-ly').

'anti-' comes from Greek 'ἀντί' via Latin and later English use; 'medieval' was formed from Medieval Latin 'medium aevum' and entered modern English usage to refer to the Middle Ages; adding '-ly' creates the adverb form 'anti-medievally'.

Initially elements meant 'against' (anti-) and 'middle age' (medieval); combined in modern use the form has come to mean 'in a way that opposes or rejects medieval ideas or styles'.