Green’s Dictionary of Slang

1. (US) a native of Kansas, spec. in the context of murderous activities carried out before and during the Civil War; also attrib.

1859		Chicago Press and Trib. 8 Feb. 2/6: The ‘posse’ came across a ‘fellow;’ they fired at him, as they said he ‘was a jayhawker.’.
1861		White Cloud Kansas Chieftain 10 Oct. n.p.: State troops have no better right to enter Kansas in hunt of Jayhawkers [...] then the Jayhawkers have to go to Missouri and help themselves to secession property.
1863		Dublin Eve. Mail 6 Oct. 3/5: The work of these ‘bushwhackers,’ ‘jayhawkers,’ and ‘red legs’ is not likely to come to an end before these once flourishing Western counties are utterly laid waste.
1872		Schele De Vere Americanisms 282: The Jayhawkers were a more offensive class of men, combining murder with marauding, and were famous before the war already, during the bloody strife carried on in Kansas.
1887		E. Custer Tenting on the Plains (rev. edn 1895) 165: Jayhawkers, bandits and bushwhackers had everything their own way for a time.
1890		Opelousas Democrat 14 June 3/2: Some did not understand what was meant by ‘Jay-hawker’ [...]. This is the name that is applied to all citizens of Kansas [DA].
1898		Globe-Republican (Kan.) 29 Dec. 1/5: I’m a Jayhawker boy from the Jayhawker state, / I wear Jayhawker hats on as Jayhawker pate, / I ride a Jayhawker horse in a Jayhawker way, / In a Jayhawker state I’m bound to stay.
1899		Monroe City Democrat (MO) 14 Sept. 2/3: The Kansas jayhawkers pillaged and scared one day and the Missouri bushwackers came in the following day and they pillaged and scared [...] the former carried the union flag, the latter the confederate flag.
1902		Knickerbocker (N.Y.) (Apr.) lix 392: Guess she must a-had Secesh beaux, / And gone to Jayhawker parties from her youth up. / This bangs the Dutch of St. Louis, / And they kin swear some.
1906		J.W. Carr ‘Words from Northwest Arkansas’ in DN III:iii 153: The Jayhawkers beat the Razorbacks by a close shave.
1906		S. Ford Shorty McCabe 30: By the time that crowd of jay-hawkers comes boomin’ down to Mother Bickell’s [...] we had the old girl up and settin’ at the front window.
1917		Daily Missourian (MO) 23 Feb. n.p.: The final football game of the Kansas-Missouri schedules witnessed the defeat of the Jayhawker machine.
1926		D. Branch Cowboy and His Interpreters 129: Daugherty and one of his cowboys, John Dobbins, were riding at the head of the herd when fifteen or twenty jayhawkers came upon them.
1930		(con. 1870s) in S. Henry Conquering Our Great Amer. Plains 326: Folks calls ’em honest farmers ’cause if they didn’t call ’em that, they couldn’t call ’em anything. All Jayhawkers!
1947		N&Q June 40/1: One small boy [...] was no doubt inspired by my brother’s Jay-hawker accent [DA].
1961		‘Kansas Jayhawker’ in Lingenfelter et al. Songs of the Amer. West (1968) 451: I’m a Jayhawker girl from a Jayhawker State.
1978		Maledicta II:1+2 (Summer/Winter) 161: Jay-hawker Any Kansan.
1987		J. Ciardi Good Words 326: Jayhawker [...] A fondly self-asserted nickname for a Kansan, the Jayhawk State.
2001		S. King Dreamcatcher 636: They were Quantrill’s boys, now; two final jayhawkers riding the western Massachusetts range.

2. (US) a rustic, a simpleton.

1904		Indian Advocate (Sacred Heart, OK) 1 Apr. 99: We speak of them wih the air of superiority with which smart city folks usually speak of rural jayhawkers and hayseeds.
1957		H.B. Allen ‘Pejorative Terms for Midwest Farmers’ in AS XXXIII:4 265: [...] jayhawk [...] jayhawker.