An Etymological Dictionary of the German Language/weil

by Friedrich Kluge

weil, conj., ‘because,’ from late MidHG. (rare) wîle; in classical MidHG. die wîle, conj., ‘so long as, during, while, since, because’ (hence ModHG. dieweil); OHG. dia wîla unz, ‘so long as’; properly accus. of Weile. —