An Etymological Dictionary of the German Language/wölben
wölben, vb., ‘to vault, arch,’ from MidHG. and OHG. węlben (from *walbian, hwalbjan), wk. vb., ‘to assume a curved shape, vault.’ Comp. OSax. bihwęlbian, ‘to arch over, cover,’ Du. welven, OIc. hvelfa, ‘to arch’; allied to AS. hwealf, ‘arched,’ and Goth. hwilftri, ‘coffin’ (lit. ‘arch’). The Teut. verbal root hwelb, hwelf, from Aryan qelp (qelq?) is related to Gr. κόλπος, ‘bosom’ (lit. ‘arch’); so too Sans. kûrcá, Lat. culcita, ‘pillow’?.