An Etymological Dictionary of the German Language/Annotated/böse

by Friedrich Kluge

böse, adjective, from the equivalent Middle High German bœse, Old High German bôsi, ‘bad, useless, slanderous.’ A word peculiar to German, not found in the other dialects; the primary meaning, judging from Old High German bôsa, ‘buffoonery,’ bôsân, ‘to vilify,’ was probably ‘speaking malevolently.’ If -si- were regarded us a suffix, Greek φαῦλος (perhaps for φαῦσ-λος), with the evolution of meaning ‘trifling, bad, wicked,’ would be connected with böse.