KayPee

KayPee or KP = Kitchen Police. Enlisted military  personnel  assigned  to  work  in  a  kitchen.

KP duties include any tedious chores in the military mess at an installation, aboard ship, or in the field, such as food preparation (but not cooking) or dish washing and pot scrubbing, sweeping and mopping floors, wiping tables, serving food on the mess line, or anything else the kitchen staff sees fit to assign to its KP crew. KP duty can be grueling because it's often added to regular duties as these kitchens normally open before and close after regular duty hours, and generate large volumes of unpleasant wastes.

KP is normally assigned out of necessity, not punishment. In this case, all junior enlisted personnel assigned to a mess are put on a roster and receive assignments to KP duty on a rotating basis.

Enlisted personnel are sometimes "put on KP" for some minor infraction committed while on duty, in uniform, or on a military installation, something that requires some form of punishment, but is not severe enough to necessitate a non-judicial punishment hearing (Article 15 / CO's, Captain's or Admiral's Mast) or court martial.

Supplemental:

The military often uses the word "police" as a verb to mean "to clean" or "to restore to order." For example, after a unit function on base, a group of enlisted persons from that unit may be assigned to police, or clean up, the location used.