'pain-sensitive' originates from Modern English as a compound of 'pain' and 'sensitive', where 'pain' ultimately derives from Latin 'poena' meaning 'punishment' or 'suffering', and 'sensitive' derives from Latin 'sensitivus' (from 'sentire') meaning 'to feel'.

'pain' changed from Latin 'poena' to Old French 'peine' and Middle English 'peine/pen' before becoming modern English 'pain'. 'sensitive' developed from Latin 'sensitivus' via Old French 'sensitif' into Middle English 'sensitive', and the compound 'pain-sensitive' is a more recent Modern English formation.

Initially 'pain' often meant 'punishment' (from Latin) but shifted to mean physical 'suffering' or 'discomfort'; 'sensitive' originally meant 'able to feel' and has retained that sense, so the compound now means 'responsive to or easily affected by pain'.