Final answer:
Illegal abolitionist voters in Kansas were known as Jayhawkers, a term stemming from the period of conflict over the Kansas-Nebraska Act and the fight over the expansion of slavery.
Step-by-step explanation:
Illegal voters in Kansas who were abolitionists were called Jayhawkers. The term 'Jayhawker' originated in the turbulent times before the American Civil War, particularly during the Kansas-Nebraska Act and subsequent events. In 1855 and 1856, Kansas was flooded with both proslavery and antislavery activists trying to influence the popular sovereignty rule of the territory.
Abolitionists from the North, who were against the expansion of slavery, came to be known as Jayhawkers, whereas proslavery activists from Missouri were often referred to as border ruffians. The tension between these groups was a prelude to the larger conflict that would engulf the United States.