Joe, were Northerners who sympathized with the South known as “Jayhawkers’’?
In antebellum Kansas, Jayhawkers were abolitionists who often clashed with pro-slavery Border Ruffians.
Today Jayhawkers are students & alumni of Kansas University.
Pre-war Northern sympathizers were called "Doughfaces", a mild form of disparagement.
During the Civil War, Northern sympathizers of Confederates were called "copperheads".
There's a long list of colorful nicknames used for various groups of that time, including Fire Eaters & Wide Awakes.