kickback (n.) Look up kickback at Dictionary.com
also kick-back, c.1900 in various mechanical senses, from kick (v.) + back (adv.). By 1926 in a slang sense of "be forced to return pelf, pay back to victims," which was extended to illegal partial give-backs of government-set wages that were extorted from workers by employers. Hence sense of "illegal or improper payment" (1932).