'fever-causing' originates from modern English as a compound of 'fever' and the present-participle 'causing'. 'fever' ultimately comes from Old English 'fēfor' (from Latin 'febris'), where 'fēfor/febris' meant 'fever/heat'; 'cause' comes via Old French from Latin 'causare', where 'caus-' meant 'to make happen/bring about'.

'fever' changed from Old English 'fēfor' (itself influenced by Latin 'febris'), and 'cause' passed from Latin 'causare' into Old French 'causer' and Middle English 'causen'; the modern English compound 'fever-causing' was formed by combining these two elements to describe something that brings about fever.

Initially, 'fever' meant 'an elevated body temperature' and 'cause' meant 'to bring about'; combined, the compound originally meant 'that which brings about fever' and has retained that core meaning, now often used adjectivally in medical usage to mean 'pyrogenic'.