1885, in the criminal psychology sense, "a morally irresponsible person," considered as mentally deranged; "one who obeys his impulses regardless of social codes," a back-formation from psychopathic.
The Daily Telegraph had, the other day, a long article commenting on a Russian woman who had murdered a little girl. A Dr. Balinsky prevailed upon the jury to give a verdict of acquittal, because she was a "psychopath." The Daily Telegraph regards this term as a new coinage, but it has been long known amongst Spiritualists, yet in another sense. [The Medium and Daybreak, Jan. 16, 1885]
The case alluded to, and Balinsky's means of procuring the acquittal, were briefly notorious in England and brought the word into currency in the modern sense.
updated on January 20, 2021