'pain-resistant' originates from English, combining the noun 'pain' (ultimately from Latin 'poena' via Old French 'peine') and the adjective 'resistant' (from Latin 'resistere' via French 'résistant'), where 'poena' meant 'punishment' and 'resistere' meant 'to stand back, oppose'.

'pain' changed from Latin 'poena' → Old French 'peine' → Middle English 'pena/pain' and eventually became modern English 'pain'. 'resistant' evolved from Latin 'resistere' → Old French 'resister' → Modern French 'résistant' and then English 'resistant', and the two were combined into the compound 'pain-resistant'.

Initially, 'pain' meant 'punishment', but over time it shifted to the meaning of 'physical suffering'; 'resistant' originally meant 'to stand against' and evolved to mean 'able to withstand', so together the compound now means 'able to withstand pain'.