"next in order after the sixth; an ordinal numeral; being one of seven equal parts into which a whole is regarded as divided;" c. 1300, from seven + -th (1), replacing earlier sevende, seveth, from Old English seofunda (Anglian, Northumbrian), seofoþa (West Saxon), from Proto-Germanic *sebundon (source also of Old Norse sjaundi, Old Saxon sivondo, Old High German sibunto, German siebente, siebte). The music note sense is from 1590s.
