A caboose is a train car that is usually at the end. If you are pulling up the rear, you could call yourself the caboose.
The engine is the first car on a freight train, and the last car is usually the caboose. Besides being last, the other feature of a caboose is its use by the crew. Most of a freight train will be filled with whatever cargo they're transporting, and they need to use that space as efficiently as possible. The caboose is where the crew can hang out during the trip. If there's a kitchen on the train, it will usually be in the caboose.