rag n.1

also rag-time, "syncopated, jazzy piano music," 1896, perhaps from rag "dance ball" (1895, American English dialect), or a shortening of ragged, in reference to the syncopated melody. Rag (n.) "ragtime dance tune" is from 1897.

If rag-time was called tempo di raga or rague-temps it might win honor more speedily. ... What the derivation of the word is[,] I have not the faintest idea. The negroes call their clog-dancing "ragging" and the dance a "rag." [Rupert Hughes, Boston Musical Record, April 1900]

Conceive the futility of trying to reduce the intangible ragness to a strict system of misbegotten grace notes and untimely rests! In attempting to perfect, and simplify, art is destroying the unhampered spirit in which consists the whole beauty of rag-time music. The very essence of rag-time is that it shall lack all art, depending for the spirit to be infused more upon the performer than upon the composer himself. [Yale Literary Magazine, June 1899]

Her first "rag-time" was "The Bully," in which she made great sport by bringing a little coloured boy on the stage with her. Miss [May] Irwin says the way to learn to sing "rag-time" is to catch a negro and study him. [Lewis C. Strang, "Famous Actresses of the Day in America," Boston, 1899]

1550s, "a coarse, heavy, woolen fabric," a word of Scandinavian origin; compare Norwegian dialectal rugga "coarse coverlet," from Old Norse rogg "shaggy tuft," from Proto-Germanic *rawwa-. Perhaps it is related to rag (n.1) and rough (adj.), and compare rugged.

The original meaning is obsolete. The sense evolved or expanded to "thick coverlet or lap-robe, heavy woolen wrap" used for various purposes (1590s), then "mat for the floor" (by 1808). The meaning "toupee" is theater slang attested by 1940.

To cut a rug "dance" is slang attested by 1942 (rug-cutter "expert dancer" is recorded by 1938). To sweep or brush something under the rug in the figurative sense of "conceal in hopes it won't be noticed or remembered" is by 1954. Figurative expression pull the rug out from under (someone) "suddenly deprive of important support" is from 1936, American English. Earlier in same sense was cut the grass under (one's) feet (1580s).