alexipyretic

The first half reaches back to Ancient Greek ἀλέξειν, alexein, "to ward off". Homeric and later Greek made that verb a ready source for compounds about defense and prevention. The second half comes from Greek πυρετός, pyretos, "fever", a common medical word by the time of Hippocrates in the 5th century BCE.

Greek physicians wrote often about πυρετός, because fever was a central sign rather than a stray symptom. Hippocrates names it repeatedly, and Galen in the 2nd century CE kept the term alive in learned medicine. That medical vocabulary later passed into Latin and then into the European scientific lexicon.

The full compound alexipyretic is a modern learned formation rather than an inherited street word. It appears in medical English in the 19th century, built from Greek parts in the same way as antiseptic and antipyretic. Its shape tells its meaning almost mechanically: something that wards off fever.

English kept the word at the edges of pharmacology and therapeutics, where precision mattered more than frequency. It never became the everyday name for a fever medicine, because antipyretic won that race. Still, alexipyretic remains transparent to anyone who knows the old Greek pieces.