An Etymological Dictionary of the German Language/Annotated/derb
derb, adjective, ‘compact, stout, blunt, uncouth,’ derived in form from Middle High German dërp (b), ‘unleavened,’ but blended in meaning with a word derbe, derb, ‘worthy, honest’ (see bieder), deduced from Old High German and Middle High German bidérbe. Middle High German dërp, Old High German dërb, ‘unleavened,’ are equiv to Old Icelandic þjarfr, Anglo-Saxon þeorf, English therf. Bieder is related to bedürfen, but derb, ‘unleavened,’ on account of its meaning, cannot belong to the same stem; it is connected rather with the root verderben.