waterbed (n.)youdaoicibaDictYouDict[waterbed 词源字典]
also water-bed, 1610s, "a bed on board a ship," from water (n.1) + bed (n.). As a water-tight mattress filled with water, it is recorded from 1844, originally for invalids to prevent bedsores. Reinvented c. 1970 as a stylish furnishing.[waterbed etymology, waterbed origin, 英语词源]