Deadpool

At some point in the distant past, a tribe of early humans hunted and fought a demon that had been preying upon them. The demon resembled a green bear, with a series of long, thin spikes protruding from its face and along its spine. The man who killed the bear was cursed by victory to assume the demon's form - his skin took on its green, decaying form, and the spikes from its face appeared on his. He gained the beast's ability to merge the limbs of others with his own body, but was shunned by the tribe he had helped to protect. Over the years, he adopted names that reflected people's reaction to him, and by the Dark Ages he had adapted the Germanic word for scare/fright, "schreck," as his name.