Origin: Unknown

Definition: noun: money paid generally to an official for covertly assisting an organization, individual, or initiative.

Example: The congressman received a ten-percent kick back for supporting the legislation that would give the mining company exclusive rights to the region.

Definition: verb: recline, as in a reclining chair.

Example: "Kick back and put your feet up," which means "Relax!"

Thanks to the Online Slang Dictionary