'fever-resistant' originates from the combination of 'fever' and 'resistant', where 'fever' refers to a high body temperature and 'resistant' means able to withstand or not be affected by something.

'Fever' comes from Old English 'fēfor', and 'resistant' comes from Latin 'resistere', meaning 'to withstand'.

Initially, 'resistant' meant 'to withstand', and this meaning has largely remained the same in modern usage.