Online Etymology Dictionary

peacock (n.): c.1300, poucock, from Middle English po "peacock" + coc (see cock (n.)).

Po is from Old English pawa "peafowl" (cock or hen), from Latin pavo (genitive pavonis), which, with Greek taos said to be ultimately from Tamil tokei (but perhaps is imitative; Latin represented the peacock's sound as paupulo).

The Latin word also is the source of Old High German pfawo, German Pfau, Dutch pauw, Old Church Slavonic pavu. Used as the type of a vainglorious person from late 14c. Its flesh superstitiously was believed to be incorruptible (even St. Augustine credits this). "When he sees his feet, he screams wildly, thinking that they are not in keeping with the rest of his body." [Epiphanus]
peahen (n.): c.1400, from Old English pawa "peafowl" (see peacock) + hen.
peak (n.): "pointed top," 1520s, variant of pike (n.4) "sharp point." Meaning "top of a mountain" first recorded 1630s, though pike was used in this sense c.1400. Figurative sense is 1784. Meaning "point formed by hair on the forehead" is from 1833. According to OED, The Peak in Derbyshire is older than the word for "mountaintop;" e.g. Old English Peaclond, for the district, Pecsaetan, for the people who settled there, Peaces ærs for Peak Cavern; sometimes said to be a reference to an elf-denizen Peac "Puck."
peak (v.): 1570s, "to rise in a peak," from peak (n.). Figurative meaning "reach highest point" first recorded 1958. Related: peaked; peaking.
peaked (adj.): "sickly-looking," 1835, from past participle of obsolete verb peak "look sickly or thin, shrink, waste away" (1540s), which is perhaps from peak in sense of "become pointed" through emaciation. Related: Peakedness.
peal (n.): mid-14c., "a ringing of a bell" especially as a call to church service, generally considered a shortened form of appeal (n.), with the notion of a bell that "summons" people to church (cf. similar evolution in peach (v.)). Extended sense of "loud ringing of bells" is first recorded 1510s.
peal (v.): 1630s, from peal (n.). Related: Pealed; pealing.
peanut (n.): 1807, earlier ground nut, ground pea (1769). The plant is native to S.America. Portuguese traders took peanuts from Brazil and Peru to Africa by 1502 and it is known to have been cultivated in Chekiang Province in China by 1573, probably arriving with Portuguese sailors who made stops in Brazil en route to the Orient. Peanut butter attested by 1892; peanut brittle is from 1894. Peanut gallery "topmost rows of a theater" is from 1874, American English; peanuts "trivial sum" is from 1934.
pear (n.): Old English pere, peru "pear," common West Germanic (cf. Middle Dutch, Middle Low German pere, Old High German pira, bira, Dutch peer), from Vulgar Latin *pera, variant of Latin pira, plural (taken for fem. singular) of pirum "pear," a loan word from an unknown source. It likely shares an origin with Greek apion "pear," apios "pear tree."
pearl (n.): mid-13c., from Old French perle (13c.) and directly from Medieval Latin perla (mid-13c.), of unknown origin. Perhaps from Vulgar Latin *pernula, diminutive of Latin perna, which in Sicily meant "pearl," earlier "sea-mussel," literally "ham, haunch, gammon," so called for the shape of the mollusk shells.

Other theories connect it with the root of pear, also somehow based on shape, or Latin pilula "globule," with dissimilation. The usual Latin word for "pearl" was margarita (see margarite).

For pearls before swine, see swine. Pearl Harbor translates Hawaiian Wai Momi, literally "pearl waters," so named for the pearl oysters found there; transferred sense of "effective sudden attack" is attested from 1942 (in reference to Dec. 7, 1941).
pearly (adj.): early 15c., from pearl + -y (2). Related: Pearliness. The pearly gates of Heaven (or the New Jerusalem) are attested by 1708, from Rev. 21:21.
peart (adj.): variant of pert (q.v.).
peasant (n.): early 15c., from Anglo-French paisant (mid-14c.), Old French paisent "local inhabitant" (12c., Modern French paysan), earlier paisenc, from pais "country, region" + Frankish suffix -enc "-ing."

Pais is from Late Latin pagensis "(inhabitant) of the district," from Latin pagus "country or rural district" (see pagan). As a style of garment in fashion (e.g. peasant blouse) from 1953.
peasantry (n.): 1550s, from peasant + -ry.
pease: Old English; see pea, of which this is the etymologically correct form.
peat (n.): c.1200, in Scottish Latin, of unknown origin, probably from a Celtic root *pett- (cf. Cornish peyth, Welsh peth "quantity, part, thing," Old Irish pet, Breton pez "piece"). The earliest sense is not of the turf but of the cut piece of it, and the Celtic root may be connected to that of piece.
peaty (adj.): 1765, from peat + -y (2). Related: Peatiness.
peavey (n.): "pointed cant hook," a lumbering hook, 1878, said to be named for a John Peavey, blacksmith in Bolivar, N.Y., who supposedly invented it c.1872. Other sources ascribe it to a Joseph Peavey of Stillwater, Maine, and give a date of 1858.
pebble (n.): small, smooth stone, late 13c., from Old English papolstan "pebblestone," of unknown origin. Perhaps imitative. Some sources compare Latin papula "pustule, pimple, swelling."
pecan (n.): 1712, paccan "the pecan tree," or a related hickory, from French pacane, from an Algonquian word meaning "nut" (cf. Cree pakan "hard-shelled nut," Ojibwa bagaan, Abenaki pagann, Fox /paka:ni/).
peccadillo (n.): "slight sin," 1590s (earlier in corrupt form peccadilian, 1520s), from Spanish pecadillo, diminutive of pecado "a sin," from Latin peccatum "a sin, fault, error," noun use of neuter past participle of peccare "to miss, mistake, make a mistake, do amiss; transgress, offend, be licentious, sin," perhaps literally "to stumble," from a PIE verbal root *ped- "to walk, stumble, fall," related to the root of foot (n.).
peccant (adj.): c.1600, from Latin peccantem (nominative pecans) "sinful," present participle of peccare "to sin" (see peccadillo). As a noun from 1620s. Related: Peccancy.
peccary (n.): pig-like animal of South America, 1610s, from Carib (Guiana or Venezuela) pakira, paquira.
peccavi (v.): 1550s, Latin, literally "I have sinned;" past tense of peccare "to sin" (see peccadillo). Related: peccavimus "we have sinned;" peccavit "he has sinned."
peck (v.): c.1300, possibly a variant of picken (see pick (v.)), or in part from Middle Low German pekken "to peck with the beak." Related: Pecked; pecking.
peck (n.1): late 13c., "dry measure of one-quarter bushel," of unknown origin; perhaps connected with Old French pek, picot (13c.), also of unknown origin (Barnhart says these were borrowed from English). Chiefly of oats for horses; original sense may be "allowance" rather than a fixed measure, thus perhaps from peck (v.).
peck (n.2): "act of pecking," 1610s, from peck (v.). It is attested earlier in thieves' slang (1560s) with a sense of "food, grub."
Peck's bad boy: "unruly or mischievous child," 1883, from fictional character created by George Wilbur Peck (1840-1916).
pecker (n.): "one who pecks," 1690s, agent noun from peck (v.); slang sense of "penis" is from 1902.
peckerwood (n.): 1859, U.S. Southern black dialectal inversion of woodpecker; in folklore, taken as the type of white folks (1929) and symbolically contrasted with blackbird.
pecking (n.): verbal noun from peck (v.), late 14c. As a behavior among hens, pecking order (1928) translates German hackliste (T.J. Schjelderuo-Ebbe, 1922); transferred sense of "human hierarchy based on rank or status" is from 1955.
peckish (adj.): "somewhat hungry," literally "disposed to peck," 1785, from peck (v.) + -ish. Related: Peckishly; peckishness.
Pecksniffian (adj.): 1851, after Mr. Pecksniff, unctuous hypocrite in Dickens' "Martin Chuzzlewit" (1844).
pectin (n.): polysaccharide found in fruit and vegetables, crucial in forming jellies and jams, 1838, from French pectine, coined early 1830s by French chemist Henri Braconnot (1781-1855) from acide pectique "pectic acid," a constituent of fruit jellies, from Greek pektikos "curdling, congealing," from pektos "curdled, congealed," from pegnynai "to make stiff or solid," from PIE root *pag-/*pak- "to join together" (see pact). Related: Pectic.
pectoral (adj.): 1570s, "pertaining to the breast," from Latin pectoralis "of the breast," from pectus (genitive pectoris) "breast, chest," from PIE root *peg- "breast."
pectoral (n.): early 15c., "ornament worn on the breast," from Middle French pectoral and directly from Latin pectorale "breastplate," noun use of neuter of adjective pectoralis (see pectoral (adj.)).

As a shortened form of pectoral muscle, attested from 1758. Slang shortening pec for this is first recorded 1966. Related: Pectorals; pecs.
peculate (v.): 1749, from Latin peculatus, past participle of peculari "to embezzle," from peculum "private property," originally "cattle" (see peculiar). Related: Peculated; peculating; peculator.
peculation (n.): 1650s, noun of action from Latin peculari (see peculate).
peculiar (adj.): mid-15c., "belonging exclusively to one person," from Latin peculiaris "of one's own (property)," from peculium "private property," literally "property in cattle" (in ancient times the most important form of property), from pecu "cattle, flock," related to pecus "cattle" (see pecuniary). Meaning "unusual" is first attested c.1600 (earlier "distinguished, special," 1580s; for sense development, cf. idiom). Related: Peculiarly.
peculiarity (n.): c.1600, "exclusive possession;" 1640s, "special characteristic," from peculiar + -ity, or else from Latin peculiaritas. Meaning "an oddity" is attested by 1777. Related: Peculiarities.
pecuniary (adj.): c.1500, from Latin pecuniarius "pertaining to money," from pecunia "money, property, wealth," from pecu "cattle, flock," from PIE root *peku- "wealth, movable property, livestock" (cf. Sanskrit pasu- "cattle," Gothic faihu "money, fortune," Old English feoh "cattle, money").

Livestock was the measure of wealth in the ancient world. For a possible parallel sense development in Old English, see fee, and cf., evolving in the other direction, cattle. Cf. also Welsh tlws "jewel," cognate with Irish tlus "cattle," connected via notion of "valuable thing."
pecunious (adj.): late 14c., from Latin pecuniosus "abounding in money," from pecunia "money" (see pecuniary). Related: Pecuniously; pecuniousness.
pedagogic (adj.): 1781, from Latin paedagogicus, from Greek paidagogikos "suitable for a teacher," from paidagogos "teacher" (see pedagogue).
pedagogical (adj.): 1610s, from Latin paedagogicus (see pedagogic) + -al (1). Related: Pedagogically.
pedagogue (n.): late 14c., "schoolmaster, teacher," from Old French pedagoge "teacher of children" (14c.), from Latin paedagogus, from Greek paidagogos "slave who escorts boys to school and generally supervises them," later "a teacher," from pais (genitive paidos) "child" (see pedo-) + agogos "leader," from agein "to lead" (see act (n.)). Hostile implications in the word are at least from the time of Pepys (1650s). Related: Pedagogal.
pedagogy (n.): 1580s, from Middle French pédagogie (16c.), from Latin paedagogia, from Greek paidagogia "education, attendance on boys," from paidagogos "teacher" (see pedagogue).
pedal (n.): 1610s, "lever (on an organ) worked by foot," from French pédale "feet, trick with the feet," from Italian pedale "treadle, pedal," from Late Latin pedale "(thing) of the foot," neuter of Latin pedalis "of the foot," from pes (genitive pedis) "foot" (see foot (n.)).

Extended to various mechanical contrivances by 1789. Pedal steel guitar is from 1969. Pedal-pushers "type of women's trousers suitable for bicycling" is from 1944.
When college girls took to riding bicycles in slacks, they first rolled up one trouser leg, then rolled up both. This whimsy has now produced a trim variety of long shorts, called "pedal pushers." ["Life," Aug. 28, 1944]
pedal (v.): 1866 of musical organs, 1888 of bicycles, from pedal (n.). Related: Pedaled; pedaling.
pedant (n.): 1580s, "schoolmaster," from Middle French pédant (1560s) or directly from Italian pedante, literally "teacher, schoolmaster," of uncertain origin, apparently an alteration of Late Latin paedagogantem (nominative paedagogans), present participle of paedagogare (see pedagogue). Meaning "person who trumpets minor points of learning" first recorded 1590s.
pedantic (adj.): formed in English c.1600, from pedant + -ic. The French equivalent is pédantesque. Perhaps first attested in John Donne's "Sunne Rising," where he bids the morning sun let his love and him linger in bed, telling it, "Sawcy pedantique wretch, goe chide Late schooleboyes." Related: Pedantical (1580s); pedantically.