Meat was originally introduced as a bloody skeleton in Mortal Kombat 4/Gold. He was the palette-swap for when kombatants were skinned alive during a fatality. However, the MK team decided to make him available as a secret costume.
Originally, he had no name or background story. The name "Meat" was givin to him by Mortal Kombat fans. However, during the events of Mortal Kombat: Armageddon, it was revealed that Meat was a horrific experiment created by Shang Tsung. However, he escaped before the sorcerer had a chance to finish him, hence his lack of skin.
Mortal Kombat: Armageddon

Meat was an experiment who escaped Shang Tsung's flesh pits before he could be completely formed. As the other kombatants fought, Meat rushed unseen to the top of the pyramid and defeated Blaze. Godlike energy enveloped him, giving him the power to shape-shift. With the ability to become anyone, Meta lost his sense of identity and disappeared into obscurity.