Explanation:

The largest dolphin species is the Orca, which is commonly known as the Killer Whale. These dolphins can be over 31 feet long when fully grown, a size which has provided them with the colloquial name of whales although they are dolphins. Because of their fierce reputation, orca are sometimes called the Ballena asesina (“assassin whale”) by the Spanish. They were referred to as “whale killers” by sailors who witnessed their attacks on larger cetaceans, and over time this name was changed to “killer whales.”