I said "the Unofficial State Song of Kansas" with my tongue firmly lodged in my cheek. But the truth be known, there was an infamous Kansas guerilla band called Jennison's Jayhawkers led by a Dr. Charles Jennison. These guys were such an embarrassment to the governor, that he mustered them into state service as the 7th Kansas Cavalry, then had them shipped off to Tennessee to get them out of his hair. The Gov. hoped that some West Point General would whip them into a proper military unit. Alas, it was not to be. They continued they jayhawking and added the word to the Civil War lexicon. The story also goes that John Brown's Body was their marching theme song; that they taught it to the rest of the army. And in their minds, they were singing about the John Brown.
PS You can read all about it in Stephen Z. Starr's book "Jennison's Jayhawkers."