'agueproof' originates from the combination of 'ague,' which comes from the Old French 'aguë,' meaning 'fever,' and 'proof,' from the Old English 'prōf,' meaning 'test' or 'resistant.'

'Aguë' transformed into the English word 'ague,' and 'prōf' became 'proof,' eventually forming the modern English word 'agueproof.'

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