'antitypical' originates from Greek and Post-classical/Modern formation, specifically from the Greek prefix 'anti-' (Greek 'anti') combined with 'typical' (from Greek 'typos' via Late Latin/Old French), where 'anti-' meant 'against' and 'typos' meant 'impression, model'.

'antitypical' was formed in English by combining the prefix 'anti-' with the adjective 'typical' (itself from Greek 'typos' through Latin/French). The compound reflects formation practices from the 17th-19th centuries when classical prefixes were commonly attached to English adjectives.

Initially it was used chiefly in theological or literary contexts to mean 'relating to an antitype' (i.e., the counterpart or fulfillment of a preceding type); over time it also acquired the more general sense 'not typical' or 'atypical'.