ledge (n.)youdaoicibaDictYouDict[ledge 词源字典]
late 13c., "crossbar on a door," perhaps from Middle English verb leggen "to place, lay" (see lay (v.)). Sense of "narrow shelf" is first recorded 1550s; "shelf-like projection of rock" is from 1550s.[ledge etymology, ledge origin, 英语词源]