1929, U.S. slang, originally in entertainment (jazz groups, dance teams), short for combination, which was used by 1924 in the sense "small instrumental band."
"good, proper, excellent," 1934, jazz slang, from American English dialectal pronunciation of right (adj.1). An identical dialectal form of the word was in 19c. English as "smooth, put in order, comb (the hair)."
late 14c., "red with heat, heated till it glows red" (of metal, etc.); in reference to persons, "lively, passionate," it is recorded from c. 1600. Red-hot mama is 1926, jazz slang, "earthy female singer," also "girlfriend, lover."
"basic facts of a situation or problem," by 1961, knitty-gritty, American English, said to have been chiefly used by black jazz musicians, perhaps ultimately from nit and grits "finely ground corn." As an adjective from 1966.