Why is the cookie cutter shark called the cookie cutter?

Cookiecutter Shark Isistius brasiliensis

Many cetaceans and large fish, including other sharks, suffer when cookiecutter sharks are around. This small, cigar-shaped shark is a parasite that bites chunks out of its prey. Using its unique thick, flexible lips to hold onto its victim by suction, it then twists itself around so that its razor-sharp lower teeth bite out a cookie-shaped piece of flesh. It is active at night, luring its victims with glowing green bioluminescent lights on its belly. It also preys on squid and crustaceans.