An Etymological Dictionary of the German Language/Holz
Holz, n., ‘wood, timber,’ from MidHG. and OHG. holz, n., ‘forest, thicket, timber.’ In the remaining dialects the meaning ‘forest’ preponderates. Comp. OIc. holt, n., ‘forest, thicket,’ so too AS. and MidE. holt, n., (wanting in E.), but Du. hout, ‘thicket, wood (as material).’ Teut. type hultos, from pre-Teut. kldos; comp. OSlov. (with a different stage of gradation) klada, f., ‘beam, wood,’ Gr. κλάδο-ς, m., ‘twig,’ OIr. caill, coill, ‘forest’ (with ll from Id).