Online Etymology Dictionary

-parous: word-forming element meaning "bearing, producing," from Latin -parus (e.g. viviparus "bringing forth young alive"), from parere "to produce, bring forth" (see pare).
-path: word-forming element used in modern formations to mean "one suffering from" (a disease or condition), from Greek -pathes, from pathos "suffering" (see pathos). Also "one versed in" (a certain type of treatment), in which cases it is a back-formation from -pathy in the related sense.
-pathic: word-forming element from Latin pathicus, from Greek pathikos "suffering, remaining passive," from pathein "to suffer" (see pathos).
-pathy: word-forming element meaning "feeling, suffering, emotion; disorder, disease," from Latin -pathia, from Greek -patheia "act of suffering, feeling" (see pathos). Meaning "system of treatment of disease" is abstracted from homeopathy (q.v.).
-phage: word-forming element meaning "eater," from stem of Greek phagein "to eat" (see -phagous).
-phagous: word-forming element meaning "eating, feeding on," from Latin -phagus, from Greek -phagos "eater of," from phagein "to eat," literally "to have a share of food," from PIE root *bhag- "to share out, apportion, distribute," also "to get a share" (cf. Sanskrit bhajati "assigns, allots, apportions, enjoys, loves," bhagah "allotter, distributor, master, lord," bhaksati "eats, drinks, enjoys;" Persian bakhshidan "to give;" Old Church Slavonic bogatu "rich").
-phane: word-forming element meaning "having the appearance of," from Greek -phanes, from phainein "to show," phainesthai "to appear" (see phantasm).
-phemia: word-forming element meaning "speech," from Greek -phemia, from pheme "speech," from stem of phemi "I speak," cognate with Latin fari "to speak," fama "report, reputation" (see fame (n.)).
-phile: also -phil, word-forming element meaning "one that loves, likes, or is attracted to," via French -phile and Medieval Latin -philus in this sense, from Greek -philos, common suffix in personal names (e.g. Theophilos), from philos "loving, dear," from philein "to love," of unknown origin.
-philia: word-forming element meaning "friendship, fondness, tendency toward," and in recent use "abnormal attraction to," from Greek philia "affection," from philos "loving," of uncertain origin. Related: -philic.
-phobe: word-forming element meaning "one who fears or hates," from French -phobe, from Latin -phobus, from Greek -phobos "fearing," from phobos "fear, panic, flight," phobein "put to flight, frighten" (see phobia).
-phobia: word-forming element meaning "excessive or irrational fear of," from Latin -phobia and directly from Greek -phobia "panic fear of," from phobos "fear" (see phobia). In widespread popular use with native words from c.1800. Related: -phobic.
-phone: word-forming element meaning "voice, sound," also "speaker of," from Greek phone "voice, sound," from PIE root *bha- (2) "to speak, say, tell" (cf. Latin for, fari "to speak," fama "talk, report;" see fame (n.)).
-phyte: word-forming element meaning "plant, plant characteristic; planting, growth; abnormal growth," from Greek phyton "plant" (see phyto-).
-plasia: word-forming element in biology and medicine denoting "formation, growth, development," from Modern Latin -plasia, from Greek plasis "molding, formation," from plassein "to mold" (see plasma).
-plasm: word-forming element meaning "a growth, a development; something molded," from Greek -plasma, from plasma "something molded or created" (see plasma).
-plast: word-forming element denoting "something made," from Greek plastos "formed, molded," verbal adjective from plassein "to mold" (see plasma). Used to form names of small particles of living matter.
-plasty: word-forming element meaning "act or process of forming," also "plastic surgery" applied to a specific part, from Greek -plastia, from plastos "molded, formed," verbal adjective from plassein "to mold" (see plasma).
-poietic: word-forming element meaning "making, producing," from Latinized form of Greek poietikos "capable of making, creative, productive," from poiein "to make, create" (see poet).
-polis: word-forming element meaning "City," from Greek polis "city" (see polis).
P: a rare letter in the initial position in Germanic, in part because by Grimm's Law PIE p- became Germanic f-; even with the early Latin borrowings in Old English, -p- takes up a little over 4 pages in J.R. Clark Hall's "Concise Anglo-Saxon Dictionary," compared to 31 pages for B and more than 36 for F. But it now is the third-most-common initial letter in the English vocabulary, and with C and S comprises nearly a third of the dictionary, a testimony to the flood of words that have entered the language since 1066 from Latin, Greek, and French.

To mind one's Ps and Qs (1779), possibly is from confusion of these letters among children learning to write. Another theory traces it to old-time tavern-keepers tracking their patrons' bar tabs in pints and quarts. But cf. also to be P and Q (1610s), "to be excellent," a slang phrase said to derive from prime quality.
p wave (n.): 1908 in geology, the p representing primary (adj.).
p.a. (n.): abbreviation of "public address" (system), attested from 1936.
P.C.: abbreviation for personal computer is from 1978; abbreviation for politically correct is by 1990.
P.C.P.: also pcp, 1960s, from animal tranquilizer phencyclidine.
P.D.Q.: also pdq, initialism for pretty damn quick, attested from 1875.
p.m.: abbreviation of Latin post meridiem "after noon."
p.o.v.: also pov, initialism for point of view, by 1973.
P.O.W.: also POW, initialism for prisoner of war, coined 1919 but not common until World War II.
P.S.: 1610s, abbreviation of Latin post scriptum (see postscript).
pa: 1804, colloquial shortening of papa (q.v.).
Pablum: See pabulum.
pabulum (n.): "food" for anything, 1670s, from Latin pabulum "fodder, food, nourishment," from PIE root *pa- "to protect, feed" (see food) + instrumentive suffix *-dhlom.

Pablum (1932), derived from this, is a trademark (Mead Johnson & Co.) for a soft, bland cereal used as a food for infants and weak and invalid people, hence figurative use (attested from 1970, first by U.S. Vice President Spiro Agnew) in reference to "mushy" political prose.
paca (n.): Central and South American rodent, 1650s, from Spanish, from Tupi (Brazil) paca.
pace (n.): late 13c., "a step in walking; rate of motion," from Old French pas "a step, pace, trace," and directly from Latin passus, passum "a step, pace, stride," noun use of past participle of pandere "to stretch (the leg), spread out," probably from PIE *pat-no-, from root *pete- "to spread" (cf. Greek petannynai "to spread out," petalon "a leaf," patane "plate, dish;" Old Norse faðmr "embrace, bosom," Old English fæðm "embrace, bosom, fathom," Old Saxon fathmos "the outstretched arms"). Also, "a measure of five feet" [Johnson]. Pace-setter in fashion is from 1895.
pace (prep.): "with the leave of," 1863, from Latin pace, ablative of pax "peace," as in pace tua "with all deference to you;" from PIE *pak- "to fasten" (see pax). "Used chiefly as a courteous or ironical apology for a contradiction or difference of opinion" [OED].
pace (v.): 1510s, "to walk at a steady rate," from pace (n.). Meaning "to measure by pacing" is from 1570s. That of "to set the pace for" (another) is from 1886. Related: Paced; pacing.
pacemaker (n.): also pace-maker, 1884, originally a rider or boat that sets the pace for others in training. Meaning "the node of the heart whivh determines the beat rate" is from 1910; sense of "man-made device for stimulating and regulating heartbeat" is from 1951. From pace (n.) + maker.
pachinko (n.): 1953, from Japanese, "pinball machine," also "slingshot, handgun," from pachin, of echoic origin, + diminutive suffix -ko.
pachyderm (n.): 1838, from French pachyderme (c.1600), adopted as a biological term 1797 by French naturalist Georges Léopole Chrétien Frédéric Dagobert, Baron Cuvier (1769-1832), from Greek pachydermos "thick-skinned," from pachys "thick, large, massive," from PIE *bhengh- "thick, fat" (cf. Sanskrit bahu- "much, numerous" Avestan bazah- "height, depth," Hittite pankush "large," Old Norse bingr "heap," Old High German bungo "a bulb," Lithuanian biess "thick") + derma "skin" (see derma).
pachysandra (n.): 1813, from Modern Latin (1803), from Greek packhys "thick" (see pachyderm) + aner (genitive andros) "man" (see anthropo-), which is used in botany to mean "stamen, having stamens."
pacific (adj.): 1540s, "tending to make peace," from Middle French pacifique, from Latin pacificus "peaceful, peace-making," from pax (genitive pacis) "peace" (see peace) + root of facere "to make" (see factitious). Meaning "peaceful, calm" is first recorded 1630s. Related: Pacifical (mid-15c.); pacifically.
Pacific Ocean: 1660, from Medieval Latin Pacificum, neuter of Latin pacificus (see pacific); so called c.1500 by Magellan when he sailed into it and found it calmer than the stormy Atlantic.
pacification (n.): "a setting at peace," early 15c., from Middle French pacification "act of making peaceful" (15c.), from Latin pacificationem (nominative pacificatio) "a peace-making," noun of action from past participle stem of pacificare "to pacify" (see pacify).
pacificism (n.): 1904, from pacific + -ism.
pacifier (n.): "one who pacifies or appeases," 1530s, agent noun from pacify. The meaning "nipple-shaped device for babies" is first recorded 1904.
pacifism (n.): 1905, from French pacifisme (by 1903, apparently coined by Émile Arnaud), from pacifique (see pacific).
pacifist (n.): 1903, from French pacifiste (see pacifism). Related: Pacifistic (1902).
pacify (v.): late 15c., "appease, allay the anger of (someone)," from Middle French pacifier "make peace," from Latin pacificare "to make peace; pacify," from pacificus (see pacific). Of countries or regions, "to bring to a condition of calm," c.1500, from the start with suggestions of submission and terrorization. Related: Pacified; pacifying.
pack (n.): "bundle," early 13c., probably from a Low German word (cf. Middle Dutch pac, pack "bundle," Middle Low German pak, Middle Flemish pac, attested from late 12c.), originally a term of wool traders in Flanders; or possibly from Old Norse pakki. All are of unknown origin.

Italian pacco is a Dutch loan word; French pacque probably is from Flemish. Meaning "set of persons" (usually of a low character) is c.1300, older than sense of "group of hunting animals" (early 15c.). Extended to collective sets of playing cards (1590s), floating ice (1791), cigarettes (1924), and submarines (1943). Meaning "knapsack on a frame" is attested from 1916. Pack of lies first attested 1763.