nitty-gritty (n.)youdaoicibaDictYouDict[nitty-gritty 词源字典]
"basic facts," 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.[nitty-gritty etymology, nitty-gritty origin, 英语词源]