How killer whales got the name 'orca'

The Orcinus orca or Orca (Killer Whale) is the largest of the dolphin family. It is a large predator that ranges from the artic ocean to the tropical seas. Their diet varies from fish to large whales and this very act of predation on large whales gave them the name "assassin whale" or "whale killer" by the Spanish. The Killer Whale like many of its dolphin brethren have such sophisticated behaviors that it may preclude culture. For more information about Orcinus orca, please visit the resources below.

Common names:
Orca
The name Orca came from the ancient Romans. The word may have been adopted from the Greek word: and is used to refer to a species of whale. Later variations of the word may have ended up to be "Orc" used to describe a large fish, whale, or sea-monster.

Killer Whale
The 18th-century Spanish sailors first called the creatures Killer Whales because of their tenacity to attack large whales. When translated into English, it changed to was mistranslated to "Killer Whale" and the name stuck.

Orca and Killer Whale:
The name "Killer Whale" is now used in English, however, the original name "Orca" has grown in popularity since the 1960s. "Orca" is still used in several other languages as well and as the amount of international research on the species increases, the names have converged to represent the creatures.

From Wikipedia:
Supporters of the original name point out that the naming heritage is not limited to Spanish sailors. Indeed the genus name "Orcinus" means "from Hell" (see Orcus), and although the name "Orca" (in use since antiquity) is probably not etymologically related, the assonance might have given some people the idea that it meant "whale that brings death," or "demon from hell." The name of this species is similarly intimidating in many other languages, including Finnish, Dutch, German, Haida, Japanese and Chinese.

Conclusion:
The name Orca and Killer Whale have come to represent the same creature and it will be interesting from a linguistic standpoint to see if the name "Orca" comes to dominate "Killer Whale" or vice versa. The name Killer Whale and Orca seem very fitting for these creatures and the roots of these names are quite interesting as well.

Resources:
http://marinebio.org/species.asp?id=84
http://en.wikipedia.org/wiki/Orca
http://www.whalesbc.com/