cracker (n.2)youdaoicibaDictYouDict
Southern U.S. derogatory term for "poor, white trash" (1766), probably an agent noun from crack (v.) in the sense "to boast" (as in not what it's cracked up to be). Compare Latin crepare "to rattle, crack, creak," with a secondary figurative sense of "boast of, prattle, make ado about."
I should explain to your Lordship what is meant by crackers; a name they have got from being great boasters; they are a lawless set of rascalls on the frontiers of Virginia, Maryland, the Carolinas and Georgia, who often change their places of abode. [1766, G. Cochrane]
But DARE compares corn-cracker "poor white farmer" (1835, U.S. Midwest colloquial). Especially of Georgians by 1808, though often extended to residents of northern Florida. Another name in mid-19c. use was sand-hiller "poor white in Georgia or South Carolina."
Not very essentially different is the condition of a class of people living in the pine-barrens nearest the coast [of South Carolina], as described to me by a rice-planter. They seldom have any meat, he said, except they steal hogs, which belong to the planters, or their negroes, and their chief diet is rice and milk. "They are small, gaunt, and cadaverous, and their skin is just the color of the sand-hills they live on. They are quite incapable of applying themselves steadily to any labor, and their habits are very much like those of the old Indians." [Frederick Law Olmsted, "A Journey in the Seaboard Slave States," 1856]
puke (n.)youdaoicibaDictYouDict
1737, "a medicine which excites vomiting;" 1966 as "material thrown up in vomiting," from puke (v.). U.S. colloquial meaning "native of Missouri" (1835) might be a different word, of unknown origin.
It is well known, that the inhabitants of the several western States are called by certain nicknames. Those of Michigan are called wolverines; of Indiana, hooshers; of Illinois, suckers; of Ohio, buckeyes; of Kentucky, corn-crackers; of Missouri pukes, &c. To call a person by his right nickname, is always taken in good part, and gives no offence; but nothing is more offensive than to mis-nickname--that is, were you to call a hoosher a wolverine, his blood would be up in a moment, and he would immediately show fight. [A.A. Parker, "Trip to the West and Texas," Concord, N.H., 1835]
Bartlett (1859) has "A nickname for a native of Missouri" as the second sense of puke (n.), the first being "A mean, contemptible fellow." The association of the state nickname with the "vomit" word is at least from 1858, and folk etymology talks of the old state literally vomiting forth immigrants to California.