Wordorigins.org

These are all contemptuous terms for white people, usually used by African Americans.

These terms are originally references to Eastern European immigrants. The origin may a blend of Hun + Polack. From the Chicago Daily Tribune of 14 May 1906:

Hun, Pole, Austrian, Bulgarian, Bohemian—the “Hunkies” of Illinois Steel colloquialism—indifferent to pain of shattered, burned, mangled body, grow frantic as the stretcher bearers near this fortress hospital.