ragyoudaoicibaDictYouDict[rag 词源字典]
rag: English has four separate words rag, none of them with very well-documented histories. The origins of the oldest, ‘rough building stone’ [13], are completely unknown. Rag ‘piece of cloth’ [14] is probably a back-formation from ragged [13], which was adapted from Old Norse roggvathr ‘tufted’. This in turn was derived from rogg ‘tuft of fur’, but no one knows where that came from. Rag ‘taunt, piece of fun’ [18] is completely mysterious, although some connection with Danish dialect rag ‘grudge’ has been suggested. And finally rag ‘syncopated jazz’ [19] is short for ragtime, which is probably an alteration of ragged time.
[rag etymology, rag origin, 英语词源]
rag (n.)youdaoicibaDictYouDict
scrap of cloth, early 14c., probably from Old Norse rögg "shaggy tuft," earlier raggw-, or possibly from Old Danish rag (see rug), or a back-formation from ragged, It also may represent an unrecorded Old English cognate of Old Norse rögg. In any case, from Proto-Germanic *rawwa-, from PIE root *reue- (2) "to smash, knock down, tear up, uproot" (see rough (adj.)).

As an insulting term for "newspaper, magazine" it dates from 1734; slang for "tampon, sanitary napkin" is attested from 1930s (on the rag "menstruating" is from 1948). Rags "personal clothing" is from 1855 (singular), American English. Rags-to-riches "rise from poverty to wealth" is attested by 1896. Rag-picker is from 1860; rag-shop from 1829.
rag (v.)youdaoicibaDictYouDict
"scold," 1739, of unknown origin; perhaps related to Danish dialectal rag "grudge." Related: Ragged; ragging. Compare bullyrag, ballarag "intimidate" (1807).