Green’s Dictionary of Slang

(US esp. army, orig. Civil War) to raid, to plunder, to steal, to operate as a guerrilla soldier; thus jayhawking, raiding.

1855		L.W. Spring Kansas 252: Legislative action [...] brought the territorial jayhawking era substantially to a close.
1863		Army Police Record in Annals of the Army of the Cumberland 519: Moore and Blue, who had become fast friends, separated, the latter going into Missouri on several jayhawking expeditions.
1864		C.W. Wills Army Life of an Illinois Soldier (1996) 231: They actually stole lots of trash right under the noses of the soldier owners. Out ‘jayhawking’ old jayhawk himself.
1874		Chicago Times 1 Jan. 5/5: George Jones jayhawked a turkey from a stall on South Clark Street on [sic] yesterday [DA].
1884		C.E. Craddock Where The Battle Was Fought 48: There’s no use in jayhawking me.
1897		W.E. Barton Hero in Homespun 218: The ‘jay-hawking’ might now be looked for at every foot of the way.
1901		Duncan & Scott Allen and Woodson Counties, Kansas 595: About this time lumber was obtained for a new school house, but I am told the greater portion of it was ‘jayhawked’ by a wagon maker who had a shop near by [DA].
1912		I. Cobb Back Home 94: He was jayhawkin’ back and forth along the State line here, burnin’ folks’ houses down over their heads.
1920		(ref. to US Civil War)Pullman Herald (WA) 10 Sept. 7/2: ‘Jayhawking’ was the term used to describe the depredations of the Kansans and they were called ‘Jayhawkers’.