An Etymological Dictionary of the German Language/Laub
Laub, n., ‘foliage,’ from the equiv. MidHG. loup(b), OHG. loub, m. and n.; a primitive and common Teut. term; comp. Goth. laufs (plur. laubôs), m., AS. leáf, n., E. leaf, Du. loof. Some connect the word with Lith. lápas, ‘leaf,’ which, however, compared with the diphthong of the Teut. word has an abnormal a (comp. Haupt with Lat. caput); Gr. λέπος, ‘scale, rind,’ is even less akin.