"the southern United States," 1859, of obscure origin, first attested in the song of that name, which was popularized, if not written, by Ohio-born U.S. minstrel musician and songwriter Dan Emmett (1815-1904); perhaps a reference to the Mason-Dixon Line, but there are other well-publicized theories dating to the Civil War. Popularized nationwide in minstrel shows. Dixieland style of jazz developed in New Orleans c. 1910, so called by 1919 (in the name of a band).
It is interesting to remember that the song which is essentially Southern — "Dixie" — and that which is essentially Northern — "Yankee Doodle" — never really had any serious words to them. [The Bookman, June 1910]
1790, "adherent or advocate of democracy," with reference to France, from French démocrate (18c., opposed to aristocrate), back-formation from démocratie (see democracy); formally revived in U.S. as a political party affiliation 1798, with a capital D. As a shortening of this, Demo (1793) is older than Dem (c. 1840). An earlier noun for "adherent of democracy" was democratian (1650s).
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<a href="https://www.etymonline.com/word/Dixiecrat">Etymology of Dixiecrat by etymonline</a>
Harper, D. (n.d.). Etymology of Dixiecrat. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/Dixiecrat