'anti-reformist' is a Modern English compound formed from the prefix 'anti-' (from Greek 'anti' meaning 'against') combined with 'reformist' (from 'reform' + suffix '-ist').

'reform' ultimately comes from Latin 'reformare' where 're-' meant 'again' and 'formare' meant 'to form'; 'reform' entered English via Old French/Medieval Latin and gave rise to 'reformist' with the agentive suffix '-ist'. 'anti-' was added in Modern English to create 'anti-reformist'.

The compound originally and primarily meant 'against reform movements or proposals'; this core meaning has remained stable as a descriptor for opposition to reforms.