Online Etymology Dictionary

pervert (v.): c. 1300 (transitive), "to turn someone aside from a right religious belief to a false or erroneous one," from Old French pervertir "pervert, undo, destroy" (12c.) and directly from Latin pervertere "overthrow, overturn," figuratively "to corrupt, subvert, abuse," literally "turn the wrong way, turn about," from per- "away" (see per) + vertere "to turn" (see versus).

Related: Perverted; perverting. Replaced native froward, which embodies the same image. Old English had mishweorfed "perverted, inverted," an identical formation to the Latin word using native elements.
pervert (n.): 1660s, "one who has forsaken a doctrine or system regarded as true, apostate," from pervert (v.). Psychological sense of "one who has a perversion of the sexual instinct" is attested from 1897 (Havelock Ellis), originally especially of homosexuals.
perverted (adj.): 1660s, "turned from the right way," past participle adjective from pervert (v.). With implied sexual sense by 1897.
pervious (adj.): "penetrable, accessible, permeable," 1610s, from Latin pervius "that may be passed through" (see impervious).
pesky (adj.): 1775, originally in New England dialect, perhaps a dialectal formation from pest (compare plaguy "confounded, annoying, disagreeable"). Partridge suggests an origin in Essex dialect.
peso (n.): "Spanish coin," 1550s, from Spanish peso, literally "a weight," from Latin pensum, properly past participle of pendere "to hang, to cause to hang" (see pendant).
pessary (n.): c. 1400, from Late Latin pessarium, from Greek pessarion "medicated tampon of wool or lint," diminutive of pessos "pessary," earlier "oval stone used in games," perhaps of Semitic origin.
pessimism (n.): 1794 "worst condition possible," borrowed (by Coleridge) from French pessimisme, formed (on model of French optimisme) from Latin pessimus "worst," originally "bottom-most," from PIE *ped-samo-, superlative of root *pes- "foot," from PIE root *ped- (1) "a foot" (see foot (n.)). As a name given to the doctrines of Schopenhauer, Hartmann, etc., that this is the worst possible world, or that everything tends toward evil, it is first recorded 1835, from German pessimismus (Schopenhauer, 1819). The attempt to make a verb of it as pessimize (1862) did not succeed.
pessimist (n.): 1820, "one who habitually expects the worst" (Knowles' dictionary, 1835, defines it as "A universal complainer"), from 19c. French pessimiste (see pessimism).
pessimistic (adj.): 1866, from pessimist + -ic.
pest (n.): 1550s (in imprecations, "a pest upon ____," etc.), "plague, pestilence," from Middle French peste (1530s), from Latin pestis "deadly contagious disease; a curse, bane," of uncertain origin. Meaning "noxious or troublesome person or thing" first recorded c. 1600.
pester (v.): 1520s, "to clog, entangle, encumber," probably a shortening of Middle French empestrer "place in an embarrassing situation" (Modern French empêtrer, Walloon epasturer), from Vulgar Latin *impastoriare "to hobble" (an animal), from Latin im- "in" + Medieval Latin pastoria (chorda) "(rope) to hobble an animal," from Latin pastoria, fem. of pastorius "of a herdsman," from pastor "herdsman" (see pastor (n.)). Sense of "annoy, trouble" (1560s) is from influence of pest. Related: Pestered; pestering.
pesticide (n.): 1939, a hybrid coined from English pest + Latinate -cide.
pestiferous (adj.): mid-15c., "mischievous, pernicious," figurative use of Latin pestiferus "that brings plague or destruction," variant of pestifer "bringing plague, destructive, noxious," from pestis "plague" (see pest) + ferre "carry" (see infer). Related: Pestiferously; pestiferousness.
pestilence (n.): c. 1300, from Old French pestilence "plague, epidemic" (12c.) and directly from Latin pestilentia "a plague, an unwholesome atmosphere," noun of condition from pestilentem (nominative pestilens) "infected, unwholesome, noxious," from pestis "deadly disease, plague" (see pest).
pestilent (adj.): late 14c., from Latin pestilentem (nominative pestilens), from pestilis "of the nature of a plague," from pestis "deadly contagious disease" (see pest (n.)). Related: Pestilently.
pestilential (adj.): late 14c., from Medieval Latin pestilentialis, from Latin pestilentia "plague" (see pestilence). Related: Pestilentially.
pestle (n.): mid-14c. (as a surname late 13c.), from Old French pestel, from Latin pistillum "pounder, pestle," related to pinsere "to pound," from PIE *pis-to-, suffixed form of root *peis- "to crush" (source also of Sanskrit pinasti "pounds, crushes," pistah "anything ground, meal," Greek ptissein "to winnow," Old Church Slavonic pišo, pichati "to push, thrust, strike," pišenica "wheat," Russian pseno "millet").
pesto (n.): olive oil-based pasta sauce, 1937, from Italian pesto, contracted form of pestato, past participle of pestare "to pound, to crush," in reference to the crushed herbs and garlic in it, from Latin root of pestle.
pet (n.1): "tamed animal," originally in Scottish and northern England dialect (and exclusively so until mid-18c.), of unknown origin. Sense of "indulged child" (c. 1500) is recorded slightly earlier than that of "animal kept as a favorite" (1530s), but the latter may be the primary meaning. Probably associated with or influenced by petty. As a term of endearment by 1849. Teacher's pet is attested from 1890. Pet-shop from 1928.
Know nature's children all divide her care;
The fur that warms a monarch warm'd a bear.
While man exclaims, 'See all things for my use!'
'See man for mine!' replies a pamper'd goose:

[Alexander Pope, "Essay on Man"]
pet (n.2): "peevishness, offense at feeling slighted," 1580s, in phrase take the pet "take offense." Perhaps from pet (n.1) on a similar notion to that in American English that gets my goat, but the underlying notion is obscure, and the form of the original expression makes this doubtful. This word seems to have been originally a southern English term, while pet (n.1) was northern and Scottish.
pet (v.): 1620s, "treat as a pet," from pet (n.1). Sense of "to stroke" is first found 1818. Slang sense of "kiss and caress" is from 1920 (implied in petting). Related: Petted.
pet peeve (n.): "thing that provokes one most," 1919, from pet (n.1) in the adjectival sense "especially cherished" (1826), here in jocular or ironic use with peeve (n.).
PETA: acronym for People for the Ethical Treatment of Animals; the group's website says it was founded in 1980.
petal (n.): 1726 (earlier petala, 1704), from Modern Latin petalum "petal" (17c.), from Greek petalon "a leaf; leaf of metal, thin plate," noun use of neuter of adj. petalos "outspread, broad, flat," from PIE root *pete- "to spread out" (see pace (n.)). Related: Petaline.
petard (n.): 1590s, "small bomb used to blow in doors and breach walls," from French pétard (late 16c.), from Middle French péter "break wind," from Old French pet "a fart," from Latin peditum, noun use of neuter past participle of pedere "to break wind," from PIE root *pezd- "to fart" (see feisty). Surviving in phrase hoist with one's own petard (or some variant) "blown up with one's own bomb," which is ultimately from Shakespeare (1605):
For tis the sport to haue the enginer Hoist with his owne petar ["Hamlet" III.iv.207].
See hoist.
petcock (n.): also pet-cock, 1864, from cock (n.2); the signification of the first element is uncertain.
Pete: familiar form of masc. proper name Peter. For Pete's sake is attested from 1903 in a list of children's expressions published in Massachusetts, probably a euphemistic use of the disciple's name in place of Christ; as an exclamation or quasi-oath, Peter! was in use 14c., but this likely is not connected to the modern use.
petechia (n.): plural petechiae, "small crimson or purple spots on skin," c. 1795 (from 1580s in English texts as an Italian word), Modern Latin, from Italian petecchia "specks or freckles on the face," in plural form petecchie "measles," of unknown origin. Related: Petechial.
Peter: masc. proper name, 12c., from Old English Petrus (genitive Pet(e)res, dative Pet(e)re), from Latin Petrus, from Greek Petros, literally "stone, rock," translation of Syriac kefa "stone" (Latinized as Cephas), nickname Jesus gave to apostle Simon Bar-Jona (Matt. xvi:17), historically known as St. Peter, and consequently a popular name among Christians (Italian Pietro, Spanish and Portuguese Pedro, Old French Pierres, French Pierre, etc.). Slang for "penis" is attested from 1902, probably from identity of first syllable.

The common form of this very common name in medieval England was Peres (Anglo-French Piers), hence surnames Pierce, Pearson, etc. Among the diminutive forms were Parkin and Perkin. To rob Peter to pay Paul (1510s, also in early 17c. French as descouvrir S. Pierre pour couvrir S. Pol) might be a reference to the many churches dedicated to those two saints, and have sprung from the fairly common practice of building or enriching one church with the ruins or revenues of another. But the alliterative pairing of the two names is attested from c. 1400 with no obvious connection to the saints:
Sum medicyne is for peter þat is not good for poul, for þe diuersite of complexioun. [Lanfranc's "Chirurgia Magna," English translation]
peter (v.): "cease, stop," 1812, of uncertain origin. To peter out "become exhausted," is 1846 as miners' slang. Related: Petered; petering.
Peter Pan (n.): name of boy-hero in J.M. Barrie's play "Peter Pan, or The Boy Who Wouldn't Grow Up" (1904). Used allusively for an immature adult man from 1914 (by G.B. Shaw, in reference to the Kaiser).
Peter Principle: 1968, "in a hierarchy, every employee tends to rise to his level of incompetence," named for (and by) Laurence Johnston Peter (1919-1990) Canadian-born U.S. educationalist and author, who described it in his book of the same name (1969).
petiole (n.): "footstalk of a leaf," 1753, from French pétiole (18c.), from Late Latin petiolus, misspelling of peciolus "stalk, stem," literally "little foot," diminutive of pediculus "foot stalk," itself a diminutive of pes (genitive pedis) "foot," from PIE root *ped- (1) "a foot" (see foot (n.)). Given its modern sense by Linnaeus.
petit (adj.): mid-14c., "trifling," from Old French petit "small, little, young, few in numbers" (11c.), probably from stem of Late Latin pitinnus "small," of uncertain origin; it corresponds to no known Latin form and perhaps is from a Celtic root pett- "part, piece, bit" also found in Italian pezza, English piece. Attested as a surname from 1086. Replaced by petty in most usages, except in established forms such as petit bourgeois "conventional middle-class" (1832; used in English by Charlotte Brontë earlier than by Marx or Engels); petit mal (1842, literally "little evil," mild form of epilepsy), and petit four (1884), which in French means "little oven," from Old French four "oven," from Latin furnus.
petit fours: see petit.
petite (adj.): "little," 1784 (from 1712 in French phrases taken into English), from French petite, fem. of petit "little" (see petit). As a size in women's clothing, attested from 1929.
petition (n.): early 14c., "a supplication or prayer, especially to a deity," from Old French peticion "request, petition" (12c., Modern French pétition) and directly from Latin petitionem (nominative petitio) "a blow, thrust, attack, aim; a seeking, searching," in law "a claim, suit," noun of action from past participle stem of petere "to make for, go to; attack, assail; seek, strive after; ask for, beg, beseech, request; fetch; derive; demand, require," from PIE root *pet-, also *pete- "to rush; to fly" (source also of Sanskrit pattram "wing, feather, leaf," patara- "flying, fleeting;" Hittite pittar "wing;" Greek piptein "to fall," potamos "rushing water," pteryx "wing;" Old English feðer "feather;" Latin penna "feather, wing;" Old Church Slavonic pero "feather;" Old Welsh eterin "bird"). Meaning "formal written request to a superior (earthly)" is attested from early 15c.
petition (v.): c. 1600, from petition (n.). Related: Petitioned; petitioning.
petitioner (n.): early 15c., from petition (n.).
Petrarchan (adj.): 1827 (Keats uses Petrarchal, 1818), from Francesco Petrarch (Italian Petrarca) the poet (1304-1374).
petrel (n.): seabird, 1670s, pitteral, modern spelling first recorded 1703 by English explorer William Dampier (1651-1715), who wrote the bird was so called from its way of flying with its feet just skimming the surface of the water, which recalls the apostle's walk on the sea of Galilee (Matt. xiv:28); if so, it likely was formed in English as a diminutive of Peter (Late Latin Petrus). If this is folk etymology, the true source of the name is undiscovered. French pétrel (1760) probably is from English.
petri dish (n.): 1892, named for German bacteriologist Julius Petri (1852-1922), who first devised it c. 1887.
petrifaction (n.): early 15c., "action or process of hardening," from petrify on model of satisfaction, etc.
petrification (n.): 1610s, from French petrification (16c.), Latinized noun of action from Middle French pétrifier (see petrify). Etymologically better than the more common petrifaction.
petrified (adj.): 1660s, "turned to stone," past participle adjective from petrify (v.). Figurative meaning "paralyzed (with fright, etc.)" is from 1720.
petrify (v.): 1590s, from Middle French pétrifier "to make or become stone" (16c.), from Latin petra "rock, crag" (see petrous) + -ficare, from facere "to make, do" (see factitious). Metaphoric sense of "paralyze with fear or shock" first recorded 1771. Related: Petrified; petrifying.
petro- (1): before vowels petr-, word-forming element used from 19c., from comb. form of Greek petros "stone," petra "rock" (see petrous).
petro- (2): word-forming element used from mid-20c. to mean "of or having to do with petroleum products," from petroleum.
petrochemical (adj.): 1913, from petro- (1) + chemical (adj.). As a noun from 1942.