'antimodernistic' originates from Greek prefix 'anti-' meaning 'against' and from English 'modernistic' (itself from 'modern'), where 'modern' ultimately traces to Latin 'modernus' (from 'modo') meaning 'just now' or 'of the present time'.

'anti-' (Greek) was appended to 'modern' in English usage to form compounds opposing modern ideas; 'modern' came into English via Old French from Latin 'modernus', and the adjective-forming suffix '-istic' (from French/Latin) produced 'modernistic' and then 'antimodernistic' as a descriptive term.

Initially, components meant 'against' + 'of the present time'; over time the compound came to mean specifically 'opposed to modernism or modern practices' and sometimes 'favoring older styles' in contemporary usage.