"sky" (poetic), Old English wolcen "cloud," also "sky, heavens," from Proto-Germanic *welk- (cognates: Old Saxon wolkan, Old Frisian wolken, Middle Dutch wolke, Dutch wolk, Old High German wolka, German Wolke "cloud," from PIE *welg- "wet" (cognates: Lithuanian vilgyti "to moisten," Old Church Slavonic vlaga "moisture," Czech vlhky "damp").