Psycho*
Psychopath – Antisocial disorder, usually manifests in aggression, perversion, criminal or amoral behaviour. Has no empathy or remorse.
Psychotic – A person affected by psychosis
Psychosis – Mental disorder, usually severe, may or may not have organic damage. Characterized by derangement of personality and loss of contact with reality. Causes deterioration of normal social functions.
Psychogenic – Mind origin, or in mental/emotional processes. Has a psychological rather than physiological origin.
Psychomotor – Relating to movement/muscular activity. Associated with mental processes/effects.
He had been dubbed Psycho, but why? Was he antisocial with no empathy or remorse (that sounded most likely), or was he named that because he never seemed to be in contact with the real world for very long (…how about no?)?
He knew he didn't have muscular problems, if one ignored the metallic arm and face, which was more to do with the fact that he lost his arm early in life, and a brown-haired woman with blue bangs damaged his face in an 'accidental' explosion.
More to the point: why did he even care about the origin of his name?