An Etymological Dictionary of the German Language/Annotated/Fieber

by Friedrich Kluge

Fieber, neuter, ‘fever,’ from the equivalent Middle High German vieber, Old High German fiebar, neuter; from Latin-Romance febris, with a change of gender as in Anglo-Saxon fêfor, neuter, equivalent to English fever; Old High German and Middle High German ie for e, as in Brief, Ziegel, Spiegel, Priester; so too Modern High German Bieber-, Middle High German biever, from vieber, with an interchange of consonants, as in Essig and Kabeljau.