seventhyoudaoicibaDictYouDict[seventh 词源字典]
c. 1300, from seven + -th (1); earlier sevende, seveth, from Old English seofunda (Anglian, Northumbrian), seofoþa (West Saxon), from Proto-Germanic *sebundon (cognates: Old Norse sjaundi, Old Saxon sivondo, Old High German sibunto, German siebente, siebte). The music note sense is from 1590s.[seventh etymology, seventh origin, 英语词源]