An Etymological Dictionary of the German Language/Hefe
Hefe, f., ‘yeast, lees, dregs,’ from MidHG. hęve, hëpfe, m. and f., OHG. hęvo, hëpfo, m. (from hëppo, hafjo, ‘yeast’); as a substance producing fermentation it is derived from the root haf, lit. ‘raising'; hence also OHG. hęvilo, MidHG. hęvel, ‘yeast,’ as well as AS. hœf, Du. hef, heffe, f., ‘yeast’ (see Hebel). Similarly Fr. levain, levûre, are related to lever. Yet OHG. hëpfo can scarcely be referred to the Aryan root kap, ‘to raise.’