1929, "drunk," past-participle adjective from piss (v.). From 1946 as "angry," from piss off.

1788, "to spray with urine" (trans.), euphemistic abbreviation of piss. Meaning "to urinate" is from 1879. Related: Peed; peeing. Noun meaning "act of urination" is attested by 1902; as "urine" by 1961. Reduplicated form pee-pee is attested by 1923.

1958, intransitive, "go away," chiefly British; the transitive meaning "annoy (someone)" is by 1968, chiefly U.S.; from piss (v.) + off (adv.). Pissed off "angry, fed up" is attested by 1946 (Partridge says 1937); said to have been used in the military in World War II; in common use from 1970s.

"chamber-pot, earthenware vessel for urine," mid-15c., pisse-pot, from piss + pot (n.1).

"of or pertaining to piss," 1926, from piss (n.) + -y (2). Figurative use as a general term of abuse is by 1972.