ragtime (n.)youdaoicibaDictYouDict[ragtime 词源字典]
also rag-time, "syncopated, jazzy piano music," 1897, 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 1899.
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]
[ragtime etymology, ragtime origin, 英语词源]