1927, shortening of psychological; 1936 (Raymond Chandler) as shortening of psychopathic (adj.).
psycho n.
1925 as short for psychologist; (earlier short for psychology, 1921); as short for psychopath by 1942.
Entries linking to psycho
psychological adj.
1680s, "of or pertaining to the mind as a subject of study;" see psychology + -ical. In early 20c. the sense gradually shifted toward "affecting or pertaining to a person's mental or emotional state." Related: Psychologically. Psychological warfare "use of propaganda, etc., to undermine an enemy's morale or resolve" is recorded from 1940. Psychological moment was in vogue from 1871, from French moment psychologique "moment of immediate expectation of something about to happen."
The original German phrase, misinterpreted by the French & imported together with its false sense into English, meant the psychic factor, the mental effect, the influence exerted by a state of mind, & not a point of time at all, das Moment in German corresponding to our momentum, not our moment. [Fowler]
psychopathic adj.
"pertaining to or of the nature of psychopathy," 1847, from psychopathy on model of German psychopatisch, from Greek psykhē "mind" (see psyche) + pathos "suffering" (from PIE root *kwent(h)- "to suffer").