as a noun, short for psychology in various senses (e.g. as an academic study, in student slang by 1895). As a verb, first attested 1917 as "to subject to psychoanalysis," short for psychoanalyze. From 1934 as "to outsmart" (also psych out); from 1963 as "to unnerve." However to psych (oneself) up is from 1972; to be psyched up is attested from 1968.
To bring to a state of keen attention; excite and incite; pump up (1957+)
Psychiatry; psychiatric: makes it down from the psych ward on the 15th floor (1940s+)
Psychology, esp as an academic study (1895+ College students)