An Etymological Dictionary of the German Language/Annotated/Unbill

by Friedrich Kluge

Unbill, feminine, ‘iniquity, wrong,’ Middle High German only; based on the cognates of billig, instead of the correct Modern High German Unbilde, feminine, Middle High German unbilde, neuter, ‘wrong, impropriety,’ which is properly an abstract from Middle High German (rare) unbil (usually unbillîch), adjective, ‘incongruous, unjust.’ On account of the meaning there is probably no direct historic connection with Bild. Compare billig, and especially Weichbild.