headlight (n.)youdaoicibaDictYouDict[headlight 词源字典]
large lamp and reflector carried in front to illuminate at night, 1861, originally of ships and locomotives, from head (n.) + light (n.). Related: Headlights, which, as slang for "a woman's breasts," is from 1940s.[headlight etymology, headlight origin, 英语词源]