The term antihero seems to have emerged in the early 1960's. I recall a comment by Psycho author Robert Bloch in a 1967 introduction, saying that a book he had written in the early 1950's came out again in a new edition, and he was surprised in the back-cover summary (written by the publisher) that the protagonist of the story he'd written as a villain, was in the new edition described a decade later as an "anti-hero". That he was disturbed by the slow warping of values over the intervening 10 years displayed in that description.
