Urochordates are called tunicates because of the leathery covering or tunic. It provides protection.

Why tunicates are named so?

The name, "tunicate" comes from the firm, but flexible body covering, called a tunic. Most tunicates live with the posterior, or lower end of the barrel attached firmly to a fixed object, and have two openings, or siphons, projecting from the other. Tunicates are plankton feeders.

What do you mean by Urochordates?

Urochordates are small marine animals with larvae that swim freely and adults that attach themselves to the ocean floor. ... Urochordates, commonly known as tunicates, differ from other chordate subphyla (Cephalochordata and Vertebrata) in that the adult form has no notochord, nerve cord, or tail.