CambridgeyoudaoicibaDictYouDict[Cambridge 词源字典]
Old English Grontabricc (c.745) "Bridge on the River Granta" (a Celtic river name, of obscure origin). The change to Cante- and later Cam- was due to Norman influence. The river name Cam is a back-formation in this case, but Cam also was a legitimate Celtic river name, meaning "crooked."[Cambridge etymology, Cambridge origin, 英语词源]