The killer whale, (Orcinus orca), is the largest member of the group of marine mammals known as dolphins (family Delphinidae). They are called killer whales because they attac â¦ k and consume whales or other large prey such as seals and sea lions.ou can thank the Greeks and the Romans for the name Orca, and the early Spanish sailors for the term Killer Whale. Ancient Romans originally applied the name Orca to these animals, possibly borrowing it from the Greek opue. One other thing, they are not really whales, but a type of dolphin.