Online Etymology Dictionary

pioneer (n.): 1520s, "foot soldier who prepares the way for the army," from Middle French pionnier "foot-soldier, pioneer," from Old French paonier "foot-soldier" (11c.), from peon (see pawn (n.2)). Figurative sense of "person who goes first or does something first" is from c. 1600. Related: Pioneers.
pioneer (v.): 1780, from pioneer (n.). Related: Pioneered; pioneering.
pious (adj.): mid-15c., from Latin pius "dutiful, devout, conscientious, religious; faithful to kindred; inspired by friendship, prompted by natural affections," perhaps [Klein] related to Latin purus "pure, clean" (see pure). Often coupled with fraud (n.) from at least 1630s. Related: Piously; piousness.
pip (n.1): "seed of an apple," 1797, shortened form of pipin "seed of a fleshy fruit" (early 14c.), from Old French pepin (13c.), probably from a root *pipp-, expressing smallness (compare Italian pippolo, Spanish pepita "seed, kernel").
pip (n.2): "disease of birds," late 14c., probably from Middle Dutch pippe "mucus," from West Germanic *pipit (source also of East Frisian pip, Middle High German pfipfiz, German Pips), an early borrowing from Vulgar Latin *pippita, unexplained alteration of Latin pituita "phlegm" (see pituitary).
pip (n.3): "spot on a playing card, etc." c. 1600, peep, of unknown origin. Because of the original form, it is not considered as connected to pip (n.1). Related: Pips.
pip-pip: slangy salutation current in Britain c. 1907-1923, said by Partridge to be in imitation of bicycle horn noise.
pipe (n.1): Old English pipe "musical wind instrument," also "tube to convey water," from Vulgar Latin *pipa "a pipe, tube-shaped musical instrument" (source also of Italian pipa, French pipe, Old Frisian pipe, German Pfeife, Danish pibe, Swedish pipa, Dutch pijp), a back-formation from Latin pipare "to chirp or peep," of imitative origin. All tubular senses ultimately derive from "small reed, whistle." Meaning "device for smoking" first recorded 1590s. Pipe-bomb attested from 1960. Pipe-cleaner recorded from 1863.
pipe (v.): Old English pipian "to play on a pipe," from Latin pipare "to peep, chirp" (see pipe (n.1)). Compare Dutch pijpen, German pfeifen. Meaning "convey through pipes" is first recorded 1887. Related: Piped; piping. Piping hot is in Chaucer, a reference to hissing of food in a frying pan; to pipe up (early 15c.) originally meant "to begin to play" (on a musical instrument); sense of "to speak out" is from 1856. Pipe down "be quiet" is from 1900, probably a reversal of this, but earlier (and concurrently) in nautical jargon it was a bo'sun's whistle signal to dismiss the men from duty (1833).
pipe (n.2): type of cask, early 14c., from Old French pipe "liquid measure, cask for wine," from a special use of Vulgar Latin *pipa "pipe" (see pipe (n.1)).
pipe dream (n.): 1870; the sort of improbable fantasy one has while smoking opium; from pipe (n.1) + dream (n.). Old English pipdream meant "piping."
pipeline (n.): 1859, "continuous line of pipes," from pipe (n.1) + line (n.). Figurative sense of "channel of communication" is from 1921; surfer slang meaning "hollow part of a large wave" is attested by 1963.
piper (n.): Old English pipere, agent noun from pipe (v.). As a kind of fish, from c. 1600. Expression pay the piper recorded from 1680s.
pipes (n.): "voice," 1580s, from pipe (n.1).
pipette (n.): also pipet, 1818, from French pipette, from Middle French pipette "tube," diminutive of Old French pipe, from Vulgar Latin *pipa (see pipe (n.1)).
pippin (n.): "excellent person or thing," 1897, from coveted varieties of apple that were raised from seed (so called since early 15c.), from Middle English pipin "seed" (see pip (n.1)).
pipsqueak (n.): also pip-squeak, 1910, from the trivial noise a young or weak creature makes.
piquancy (n.): 1660s, from piquant + -cy.
piquant (adj.): 1520s, from Middle French piquant "pricking, stimulating, irritating," present participle of piquer "to prick, sting, nettle" (see pike (n.2)).
pique (n.): 1530s, "fit of ill feeling," from Middle French pique "a prick, sting, irritation," noun of action from piquer (see pike (n.2)).
pique (v.): "to excite to anger," 1670s, from French piquer "to prick, sting" (see pike (n.2)). Softened meaning "to stimulate, excite" is from 1690s. Related: Piqued; piquing.
piquet (n.): card game, 1640s, from French piquet, picquet (16c.), of uncertain origin, perhaps a diminutive of pic "pick, pickaxe, pique," from phrase faire pic, a term said to be used in the game.
piracy (n.): early 15c., from Medieval Latin piratia, from Greek peirateia "piracy," from peirates (see pirate (n.)).
piranha (n.): also pirana, 1869, from Portuguese piranha, from Tupi (Brazil) pira nya, variant of pira'ya, literally "scissors."
pirate (n.): c. 1300 (mid-13c. as a surname), from Latin pirata "sailor, corsair, sea robber" (source also of Spanish, Italian pirata, Dutch piraat, German Pirat), from Greek peirates "brigand, pirate," literally "one who attacks" (ships), from peiran "to attack, make a hostile attempt on, try," from peira "trial, an attempt, attack," from PIE *per-ya-, suffixed form of root *per- (3) "to try, risk," (source also of Latin experiri "to try;" Greek empeiros "experienced;" Old Irish aire "vigilance;" Gothic ferja "watcher;" Old English fær "danger, calamity"). According to Watkins, this is "A verbal root belonging to the group of" *per- (1) "forward, through" (see per) via the notion of "to lead over, to press forward."

An Old English word for it was sæsceaða. Meaning "one who takes another's work without permission" first recorded 1701; sense of "unlicensed radio broadcaster" is from 1913.
pirate (v.): 1570s, from pirate (n.). Related: Pirated; pirating.
piratical (adj.): 1570s, from Latin piraticus "pertaining to pirates," from Greek peiratikos, from peirates "pirate" (see pirate (n.)) + -ical. Related: Piratically (1540s).
pirl (v.): c. 1500 (implied in pirled) "to twist, wind" (thread, etc.), of unknown origin. Related: Pirling.
pirogi (n.): 1854, from Yiddish, from Russian, plural of pirog "pie," perhaps borrowed from the Turkic language of the Kazan Tatars (compare Turkish borek).
pirogue (n.): 1660s, from French pirogue, probably from Galibi (a Carib language) piragua "a dug-out." Compare Spanish piragua (1530s).
pirouette (n.): 1706, from French pirouette "spinning top; pirouette in dancing," from Middle French pirouet "spinning top" (15c.), from Gallo-Roman root *pir- "peg, plug" (source of Italian piruolo "peg top") + diminutive suffix -ette.
pirouette (v.): 1822, from pirouette (n.) and also from French pirouetter. Related: Pirouetted; pirouetting.
pis aller (n.): "last resource, what one would do at the worst," 1670s, French, literally "to go worse," from pis "worse," from Latin peius, neuter of peior "worse" (see pejorative) + aller "to go."
Pisa: Italian city, from Etruscan, of uncertain meaning. Related: Pisan.
piscatology (n.): 1867, a hybrid from Latin piscatus, past participle of piscari "to fish," from pisces "a fish" (see fish (n.)) + -ology.
piscatorial (adj.): 1750, from piscatory + -ial.
piscatory (adj.): 1630s, from Latin piscatorius "of fishermen," from piscator "fisherman," from piscari "to fish," from pisces "a fish" (see fish (n.)).
Pisces (n.): 12th sign of the zodiac, late Old English, from Latin pisces, from plural of piscis "a fish," cognate with Gothic fisks, Old English fisc (see fish (n.)). Applied to persons born under this sign from 1924.
piscine (n.): c. 1300, "reservoir, bathing pool," from Old French piscine "fishpond," from Latin piscina, from piscis "a fish" (see fish (n.)). Ecclesiastical sense is from late 15c., from Medieval Latin piscina. As an adjective from 1799.
piscivorous (adj.): 1660s, from Latin piscis "fish" (see fish (n.)) + -vorous.
Pisgah: 1640s, name of the mountain east of the River Jordan, whence Moses was allowed to view the Promised Land he could not enter (Deut. iii:27); with figurative extension. From Hebrew, literally "cleft."
pish: exclamation of contempt, attested from 1590s.
pismire (n.): "ant," late 14c. (early 14c. as a surname), from pyss "urine" (said to be in reference to the acrid smell of an anthill) + mire "an ant," probably from Old Norse maurr "ant" (cognate with Swedish myra, Danish myre, Middle Dutch miere, Dutch mier, Crimean Gothic miera "ant"), from PIE base *morwi- (see Formica (2)). Compare pissant, also early Dutch mierseycke (from seycke "urine"), Finnish kusiainen (from kusi "urine").
He is as angry as a pissemyre,
Though þat he haue al that he kan desire.
[Chaucer]
Applied contemptuously to persons from 1560s.
piss (v.): late 13c., from Old French pissier "urinate" (12c.), from Vulgar Latin *pissiare, of imitative origin. To piss away (money, etc.) is from 1948. Related: Pissed; pissing. Pissing while (1550s) once meant "a short time."
He shall not piss my money against the wall; he shall not have my money to spend in liquor. [Grose, "Classical Dictionary of the Vulgar Tongue," 3rd edition, 1796]
piss (n.): late 14c., from piss (v.). As a pure intensifier (piss-poor, piss-ugly, etc.) it dates from World War II. Piss and vinegar first attested 1942. Piss-prophet "one who diagnosed diseases by inspection of urine" is attested from 1620s. Piss proud "erect upon awakening" is attested from 1796.
piss off (v.): (intransitive) "go away," 1958, chiefly British; (transitive) "annoy," 1968, chiefly U.S.; from piss (v.) + off. 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.
piss-pot (n.): mid-15c., from piss + pot (n.1).
pissant (n.): 1660s, "an ant," from first element of pismire (q.v.) + ant. Meaning "contemptible, insignificant person" is from 1903.
[B]y sun-down [the gals] come pourin out of the woods like pissants out of an old log when tother end's afire. ["Dick Harlan's Tennessee Frolic," in collection "A Quarter Race in Kentucky," Philadelphia, 1846]
pissed (adj.): 1929, "drunk," past participle adjective from piss (v.). From 1946 as "angry," from piss off.
pissy (adj.): 1926, from piss + -y (2). Figurative use by 1972.