Resistant to or protected against ague; not susceptible to fever and chills.
From 'ague' plus 'proof' (resistant to), a compound adjective created by medical practitioners and herbalists seeking to describe cures or preventatives against historical fevers.
Medieval herbalists would advertise their remedies as 'agueproof,' and this word shows how pre-scientific medicine created marketing language for treatments that were mostly useless—a linguistic fossil of false medical confidence from centuries past.
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