King Piccolo

King Piccolo (ピッコロ大魔王, Pikkoro Daimaō; lit. "Piccolo the Great Demon King") is a character from the anime and manga series Dragon Ball, and appears from time to time in a couple flashbacks of Dragon Ball Z. He is introduced as a Mazoku (Demon) in the story who once precipitated the Earth into utter mayhem and pandemonium, spawning an army of animal-like Namekian sons and converting a peaceful planet into a living hell. Later, it is revealed that he is the evil counter-part of Kami; the two were once a single entity. King Piccolo's name is a dual-layered pun: based on the instrument of the same name (hence, all of his sons share the names of various musical instruments), but also the Japanized English pronunciation of "pickle" matching the food-themed names of other characters as well as his green coloring.
King Piccolo came into being some 300 years before the beginning of Dragon Ball sometime after a nameless Namek on Earth attempted to assume the position of guardian of Earth, he was denied the position due to the evil that occulted within (a guardian's motives must be pure, but the nameless Namek also wanted the job for the power it brought). As a result, the Namekian concentrated and trained to relinquish the evil within; which conspired into producing two separate entities — if one should perish, the other would also. This resulted in two beings — the concentrated evil being known as King Piccolo, and the pure being known as Kami. At first, the name "Piccolo" was a reference to the wind instrument, but then a revelation by Mr. Popo to Bulma meant it translated to "different world" in Namekian.

Information from:
http://dragonball.wikia.com/