Plunder can mean stolen goods or money obtained illegally, like plunder that thieves hide somewhere, or the act of taking those things — a burglar who plunders the jewelry store.
Plunder is an old Middle High German word that originally meant "household goods and clothes": in other words, your stuff. During the Thirty Years' War (1618-1648), English speakers acquired this word while fighting in the land that is today Germany, but with the added meaning of taking the plunder as, well, plunder. As both a noun and verb, a synonym for plunder is loot.
