'reform-resistant' originates from Modern English, formed by compounding the noun/verb 'reform' and the adjective 'resistant'. 'reform' ultimately comes from Latin 'reformare' where 're-' meant 'again' and 'formare' meant 'to form'; 'resistant' comes via French from Latin 'resistere', where 're-' meant 'back' and 'sistere' (or sistere-like root) meant 'to stand'.

'reform' passed into English via Old French/Middle English (e.g. Old French 'reformer', Middle English 'reformen') and became English 'reform'; 'resistant' came into English from French 'résistant' (modern French) which traces back to Latin 'resistere' and the past-participial/adjectival forms that produced the English adjective 'resistant'. The compound 'reform-resistant' is a modern English formation combining the two elements.

Initially, 'reform' meant 'to form again' (Latin) and shifted toward the sense of 'making changes or improvements' in modern usage; 'resistant' originally carried the sense of 'standing back' or 'withstanding' and evolved into 'opposed to or not easily affected by' — together yielding the current sense 'opposed to reforms or not easily changed by them.'