An Etymological Dictionary of the German Language/Annotated/weil

by Friedrich Kluge

weil, conjunction, ‘because,’ from late Middle High German (rare) wîle; in classical Middle High German die wîle, conjunction, ‘so long as, during, while, since, because’ (hence Modern High German dieweil); Old High German dia wîla unz, ‘so long as’; properly accusative of Weile. —