The term was created by pirates in the late 13th century, BC. Booty refers to a Pirate's "treasure" such as gold, chains, penor's etc. The clapping refers to an action that occurs after the "booty" was discovered. Pirates tend to clap in joy when a booty is found. Booty clap.
Bobby the Pirate Booty Clap near the Atlantic Ocean when he found a golden pimp cup at the bottom of the ocean.