cloud: [OE] In Old English the word for ‘cloud’ was weolcen (whence modern English welkin, a poetical term for ‘sky’), which is related to German wolke ‘cloud’. At that time Old English clūd, the ancestor of cloud, meant ‘mass of rock, hill’ (it is probably related to clod). As applied to ‘clouds’, presumably from a supposed resemblance between cumulus clouds and lumps of earth or rock, it dates from the 13th century. => clod[cloud etymology, cloud origin, 英语词源]