Online Etymology Dictionary

peter (v.): "cease, stop," 1812, of uncertain origin. To peter out "become exhausted," is 1846 as miners' slang. Related: Petered; petering.
Peter Pan: 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" (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" (cf. 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.
petrodollar (n.): 1974, "surplus of petroleum exports over imports of all other goods," as a notational unit of currency (in reference to OPEC nations), formed in English from petro- (2) + dollar.
petroglyph (n.): 1870, from French pétroglyphe, from Greek petra "rock" (see petrous) + glyphe "carving" (see glyph).
petrol (n.): "gasoline," 1895, from French pétrol (1892); earlier used (1580s) in reference to the unrefined substance, from Middle French petrole "petroleum," from Old French (13c.), from Medieval Latin petroleum (see petroleum).
petroleum (n.): early 15c. "petroleum, rock oil" (mid-14c. in Anglo-French), from Medieval Latin petroleum, from Latin petra "rock" (see petrous) + oleum "oil" (see oil (n.)).
petrology (n.): 1811 (erroneously as petralogy), from petro- (1) "rock" + -ology.
Petronilla: also Petronella, fem. proper name, a feminine diminutive of Latin Petronius. Also "the name of a saint much-invoked against fevers and regarded as a daughter of St. Peter. The name was accordingly regarded to be a derivative of Peter and became one of the most popular of girls' names, the vernacular Parnell being still used as a proper name as late as the 18th century in Cornwall" [Reaney].
petrous (adj.): 1540s, from Middle French petreux, from Latin petrosus "stony," from petra "rock," from Greek petra "rock, cliff, ledge, shelf of rock, rocky ridge," of uncertain origin. Possibly from PIE root *per- "to lead, pass over," if the original meaning is "bedrock" and the notion is "what one comes through to" [Watkins].
petticoat (n.): early 15c., pety coote, literally "a small coat," from petty + coat (n.). Originally a padded coat worn by men under armor, applied mid-15c. to a garment worn by women and young children. By 1590s, the typical feminine garment, hence a symbol of female sex or character.
Men declare that the petticoatless female has unsexed herself and has left her modesty behind. ["Godey's Magazine," April 1896]
pettifogger (n.): 1560s, from petty; the second element possibly from obsolete Dutch focker, from Flemish focken "to cheat," or from cognate Middle English fugger, from Fugger the renowned family of merchants and financiers of 15c.-16c. Augsburg. In German, Flemish and Dutch, the name became a word for "monopolist, rich man, usurer."
A 'petty Fugger' would mean one who on a small scale practices the dishonourable devices for gain popularly attributed to great financiers; it seems possible that the phrase 'petty fogger of the law,' applied in this sense to some notorious person, may have caught the popular fancy. [OED first edition, in a rare burst of pure speculation]
However, OED also calls attention to pettifactor "legal agent who undertakes small cases" (1580s), which, though attested slightly later, might be the source of this. Related: Pettifoggery.
pettifogging: 1570s as a verbal noun; c.1600 as a past participle adjective; see pettifogger. A verb pettifog is rare and attested only from 1640s.
petting (n.): 1873, "fondling indulgence," verbal noun from pet (v.). Meaning "amorous caressing, foreplay" is from 1920 (in F. Scott Fitzgerald).
pettish (adj.): 1550s, "impetuous," evidently from pet (n.2) in its "ill humor" sense + -ish. Meaning "peevish, easily annoyed" is from 1590s.
It has naturally been assoc. with PET sb.1, as being a characteristic habit of a "pet" or indulged and spoiled child; but the connexion of sense is not very clear or simple .... [OED]
Related: Pettishly; pettishness.
petty (adj.): late 14c., "small," from phonemic spelling of Old French petit "small" (see petit). In English, not originally disparaging (cf. petty cash, 1834; petty officer, 1570s). Meaning "of small importance" is recorded from 1520s; that of "small-minded" is from 1580s. Related: Pettily; pettiness. An old name for "Northern Lights" was petty dancers.
petulance (n.): c.1600, "insolence, immodesty," from French pétulance (early 16c.), from Latin petulantia "sauciness, impudence," noun of quality from petulantem (see petulant). Meaning "peevishness" is recorded from 1784, from influence of pettish, etc. It displaced earlier petulancy (1550s).
petulant (adj.): 1590s, "immodest, wanton, saucy," from Middle French petulant (mid-14c.), from Latin petulantem (nominative petulans) "wanton, froward, saucy, insolent," present participle of petere "to attack, assail; strive after; ask for, beg, beseech" (see petition (n.)). Meaning "peevish, irritable" first recorded 1775, probably by influence of pet (n.2). Related: Petulantly.
petunia (n.): 1825, from Modern Latin Petunia (1789), from French petun (16c.), an obsolete word for "tobacco plant," from Portuguese petum, from Guarani (Paraguay) pety. It has a botanical affinity to the tobacco plant. The word first is recorded (in German) as bittin; it survives as the regular word for tobacco only in Breton butun, but it was in use in English in 17c.
Many haue giuen it the name, Petum, whiche is in deede the proper name of the Hearbe, as they whiche haue traueiled that countrey can tell. [John Frampton, translation of Nicolás Monardes' "Joyful Newes Oute of the Newe Founde Worlde," 1577]
pew (n.): late 14c., "raised, enclosed seat for certain worshippers" (ladies, important men, etc.), from Old French puie, puy "balcony, elevation," from Latin podia, plural of podium "elevated place," also "balcony in a Roman theater" (see podium). Meaning "fixed bench with a back, for a number of worshippers" is attested from 1630s.
pewee (n.): "flycatcher, lapwing," 1810, variant of pewit (q.v.). See also peewee.
pewit (n.): "lapwing" (still the usual name for it in Scotland), 1520s, imitative of its cry (cf. Flemish piewit-voghel, Middle Low German kivit, German kiwitz; also see kibitz).
pewter (n.): early 14c., "any of various alloys having tin as their main constituent" (the usual form is one part lead to four parts tin), from Old French peautre (12c.), from Vulgar Latin *peltrum "pewter" (source of Spanish peltre, Italian peltro), of uncertain origin. Related: Pewterer.
peyote (n.): "mescal cactus," 1849, from Mexican Spanish peyote, from Nahuatl peyotl, said to mean "caterpillar;" the cactus so called from the downy button on top.
Pez: Austrian candy product, in U.S. use by 1956, said to be from letters in German Pfefferminz "peppermint."
pH: 1909, from German PH, introduced by S.P.L. Sörensen, from P, for German Potenz "potency, power" + H, symbol for the hydrogen ion that determines acidity or alkalinity.
ph: now in English usually representing "f," originally it was the combination used by Romans to represent Greek letter phi (cognate with Sanskrit -bh-, Germanic -b-), which at first was an aspirated "p," later the same sound as German -pf-. But by 2c. B.C.E. had become a simple sound made by blowing through the lips (bilabial spirant).

Roman "f," like modern English "f," was dentilabial; by c.400, however, the sounds had become identical and in some Romanic languages (Italian, Spanish), -ph- regularly was replaced by -f-. This tendency took hold in Old French and Middle English, but with the revival of classical learning the words subsequently were altered back to -ph- (except fancy and fantastic), and due to zealousness in this some non-Greek words in -f- began to appear confusedly in -ph-, though these forms generally have not survived.
Ph.D: attested from 1869; abbreviation of Latin Philosophiae Doctor "Doctor of Philosophy."
phaeton (n.): type of light four-wheeled carriage, 1742, from French (1735), from Greek Phaethon name of the son of Helios and Clymene, who tried to drive his father's sun-chariot but crashed after almost setting fire to the whole earth. His name is literally "shining," from phaein "to shine, gleam," from phaos "light" (see fantasy). Earlier as a name for a reckless driver (1590s).
phage (n.): virus that destroys bacteria, 1917, an abbreviated form of bacteriophage.
phago-: word-forming element meaning "eating," from Greek phago- "eating, devouring," (see -phagous).
phagocyte (n.): 1884, from German phagocyten (plural), coined in German in 1884 by Dr. Elias Metchnikoff (1845-1916) from Greek phago- "eating, devouring" (see -phagous) + -cyte (see cyto-). Related: Phagocytosis.
phalange (n.): mid-15c., "phalanx, ancient military division," from Middle French phalange "phalanx" (13c.), from Latin phalangem (nominative phalanx); see phalanx. It is the earlier form of this word in English.