Online Etymology Dictionary

pentad (n.): 1650s, from Greek pentas (genitive pentados) "group of five" (see five). Meaning "period of five years" is from 1880; meaning "period of five days" is from 1906, originally in meteorology.
pentagon (n.): plane figure with five angles and five sides, 1560s, from Middle French pentagone or directly from Late Latin pentagonum "pentagon," from Greek pentagonon, noun use of neuter of adjective pentagonos "five-angled," from pente "five" (see five) + gonia "angle" (see knee (n.)). The U.S. military headquarters Pentagon was completed 1942, so called for its shape; used allusively for "U.S. military leadership" from 1945. Related: Pentagonal.
pentagram (n.): "five-pointed star," 1820, from Greek pentagrammon, noun use of neuter of adj. pentagrammos "having five lines," from pente "five" (see five) + gramma "what is written" (see grammar).
pentameter (adj.): 1540s, from Middle French pentametre, from Latin pentameter, from Greek pentametros (adj.) "having five measures," from pente "five" (see five) + metron "meter" (see meter (n.2)). As a noun from 1580s.
pentangle (n.): c.1300; see penta- + angle (n.). In some early uses perhaps a corruption of pentacle. Related: Pentangular.
Pentateuch: first five books of the Bible, c.1400, from Late Latin pentateuchus (Tertullian, c.207), from Greek pentateukhos (c.160), originally an adjective (abstracted from phrase pentateukhos biblos), from pente "five" (see five) + teukhos "implement, vessel, gear" (in Late Greek "book," via notion of "case for scrolls"), literally "anything produced," related to teukhein "to make ready," from PIE *dheugh- "to produce something of utility" (see doughty).
pentathlon (n.): athletic contest of five events, 1852, from Greek pentathlon "the contest of five exercises," from pente "five" (see five) + athlon "prize, contest," of uncertain origin. Earlier in English in Latin form pentathlum (1706). The Greek version consisted of jumping, sprinting, discus and spear throwing, and wrestling. The modern version (1912) consists of horseback riding, fencing, shooting, swimming, and cross-country running.
Pentecost: Old English Pentecosten "Christian festival on seventh Sunday after Easter," from Late Latin pentecoste, from Greek pentekoste (hemera) "fiftieth (day)," fem. of pentekostos, from pentekonta "fifty," from pente "five" (see five). The Hellenic name for the Old Testament Feast of Weeks, a Jewish harvest festival observed on 50th day of the Omer (see Lev. xxiii:16).
pentecostal: 1660s, "pertaining to the Pentecost," from Latin pentecostalis (Tertullian), from pentecoste (see pentecost). With a capital P- and meaning "Pentecostalist," in reference to "Christian sect emphasizing gifts of the Holy Spirit" (Acts ii), it is attested from 1904 (noun and adjective).
penthouse (n.): pendize, early 14c., from Anglo-French pentiz, a shortening of Old French apentis "attached building, appendage," from Medieval Latin appendicium, from Latin appendere "to hang" (see append). Modern spelling is from c.1530, by folk etymology influence of Middle French pente "slope," and English house (the meaning at that time was "attached building with a sloping roof or awning"). Originally a simple structure (Middle English homilies describe Jesus' birthplace in the manger as a "penthouse"); meaning "apartment or small house built on the roof of a skyscraper" first recorded 1921, from which time dates its association with luxury.
Pentothal: trademark name of an anaesthetic and hypnotic, 1935, refashioning of Thiopental, from pento-, in reference to the methylbutyl five-carbon group + first two letters of thiobarbiturate + chemical product suffix -ol.
penult (adj.): "last but one," 1530s, abbreviation of penultima. As a noun from 1570s.
penultima (n.): 1580s, from Latin penultima (syllaba), "the next to the last syllable of a word or verse," from fem. of Latin adjective penultimus "next-to-last," from paene "almost" + ultimus "final" (see ultimate).
penultimate (adj.): 1670s, from penultima (n.) on model of proximate.
penumbra (n.): 1660s, from Modern Latin penumbra "partial shadow outside the complete shadow of an eclipse," coined 1604 by Kepler from Latin pæne "almost" + umbra "shadow" (see umbrage). Related: Penumbral.
penurious (adj.): 1590s, from penury + -ous, or else from Medieval Latin penuriosus, from Latin penuria "penury." Originally "poverty-stricken, in a state of penury;" meaning "stingy" is first attested 1630s. Related: Penuriously.
penury (n.): c.1400, from Latin penuria "want, need; scarcity," related to paene "scarcely."
Penzance: place in Cornwall, Pensans (late 13c.), literally "Holy Headland," from Cornish penn "head" + sans "holy."
peon (n.): unskilled worker, 1826, from Mexican Spanish peon "agricultural laborer" (especially a debtor held in servitude by his creditor), from Spanish peon "day laborer," also "pedestrian," originally "foot soldier," from Medieval Latin pedonem "foot soldier" (see pawn (n.2)). The word entered British English earlier (c.1600) in the sense "native constable, soldier, or messenger in India," via Portuguese peao "pedestrian, foot soldier, day laborer."
peonage (n.): 1848, American English, from peon + -age.
peony (n.): a 16c. merger of Middle English pyony (from Old English peonie) and Old North French pione (Modern French pivoine), both from Late Latin peonia, from Latin pæonia, from Greek paionia (fem. of paionios), perhaps from Paion, physician of the gods (or Apollo in this aspect), and so called for the plant's healing qualities. The root, flowers, and seeds formerly were used in medicine.
people (n.): late 13c., "humans, persons in general," from Anglo-French people, Old French peupel "people, population, crowd; mankind, humanity," from Latin populus "a people, nation; body of citizens; a multitude, crowd, throng," of unknown origin, possibly from Etruscan. The Latin word also is the source of Spanish pueblo, Italian popolo. In English, it displaced native folk.

Meaning "body of persons comprising a community" first recorded late 13c. in Anglo-French; meaning "common people, masses" (as distinguished from the nobility) first recorded c.1300 in Anglo-French. Meaning "one's own tribe, group, etc." is from late 14c. The word was adopted after c.1920 by Communist totalitarian states to give a spurious sense of populism to their governments. Legal phrase The People vs., in U.S. cases of prosecution under certain laws, dates from 1801. People of the Book "those whose religion entails adherence to a book of divine revelation (1834) translates Arabic Ahl al-Kitab.
people (v.): late 15c. (intransitive), c.1500 (transitive), from people (n.), or else from Middle French peupler, from Old French peuple. Related: Peopled; peopling.
Peoria: small city in Illinois, U.S., originally the name of a subdivision of the Miami/Illinois people (1673), from native /peewaareewa/. Their own name is said to mean "carriers." The place name also is found in Oklahoma and Iowa, but it is the Illinois city that has been proverbially regarded as the typical measure of U.S. cultural and intellectual standards at least since Ambrose Bierce (c.1890). Also the butt of baseball player jokes (c.1920-40, when it was part of the St. Louis Cardinals farm system) and popularized in the catchphrase "It'll play in Peoria" (often negative), meaning "the average American will approve," which was popular in the Nixon White House (1969-74) but seems to have had a vaudeville origin. Personification in "little old lady in Peoria" is said to be from Harold Ross of the "New Yorker." Peoria's rivals as embodiment of U.S. small city values and standards include Dubuque, Iowa; Hoboken and Hackensack, N.J.; Oakland (Gertrude Stein: "When you get there, there isn't any there there") and Burbank, Calif., and the entire state of North Dakota.
pep (n.): "vigor, energy," 1912, shortened form of pepper (n.), which was used in the figurative sense of "spirit, energy" from at least 1847. Pep rally is attested from 1945; pep talk from 1926. To pep (something) up is from 1925.
pepper (n.): Old English pipor, from an early West Germanic borrowing of Latin piper "pepper," from Greek piperi, probably (via Persian) from Middle Indic pippari, from Sanskrit pippali "long pepper." The Latin word is the source of German Pfeffer, Italian pepe, French poivre, Old Church Slavonic pipru, Lithuanian pipiras, Old Irish piobhar, Welsh pybyr, etc. Application to fruits of the capsicum family (unrelated, originally native of tropical America) is 16c.
pepper (v.): "to sprinkle as with pepper," 1610s, from pepper (n.). Old English had gepipera. Meaning "to pelt with shot, etc." is from 1640s. Related: Peppered; peppering.
pepper-box (n.): 1540s, from pepper (n.) + box (n.1). Meaning "hot-tempered person" is from 1867.
pepper-pot (n.): 1838, from pepper (n.) + pot (n.1).
peppercorn (n.): late Old English, from pepper (n.) + corn (n.1).
peppermint (n.): 1690s, from pepper (n.) + mint (n.1). As a type of candy drop by 1829.
pepperoni (n.): "beef and pork sausage seasoned with pepper," 1919, American English, from Italian peperone "chilli," from pepe (see pepper (n.)).
peppery (adj.): 1690s, from pepper (n.) + -y (2). Figurative use from 1826. Related: Pepperiness.
peppy (adj.): "full of pep," 1915, from pep + -y (2).
Pepsi-Cola: U.S. patent filed Sept. 23, 1902, by Caleb D. Bradham (1867-1934), pharmacist and drugstore owner of New Bern, N.C., probably from pepsin; early Pepsi ads tout it as a digestive aid.
pepsin (n.): also pepsine, fermin in gastric juice, used medicinally for cases of indigestion, 1844, coined in German (Theodor Schwann, 1835) from Greek pepsis "digestion," from stem pep- (see peptic) + -in (2).
peptic (adj.): 1650s, from Latin pepticus, from Greek peptikos "able to digest," from peptos "cooked, digested," verbal adjective of peptein "to cook" (see cook (n.)).
peptide (n.): 1906, from German peptid; see peptone + -ide, probably indicating a derivative.
peptone (n.): 1860, from German Pepton, from Greek pepton, neuter of peptos "cooked, digested" (see peptic).
per (prep.): 1580s (earlier in various Latin and French phrases), from Latin per "through, during, by means of, on account of, as in," from PIE root *per- (1) "Base of prepositions and preverbs with the basic meanings of 'forward,' 'through,' and a wide range of extended senses such as 'in front of,' 'before,' 'early,' 'first,' 'chief,' 'toward,' 'against,' 'near,' 'at,' 'around'" [Watkins]. Cf. Sanskrit pari- "around, about, through," pura "before, formerly;" Avestan pairi- "around," paro "before;" Old Persian pariy; Hittite para- "on, forth;" Greek peri "around, about, near, beyond," paros "before," para "from beside, beyond," pro "before;" Latin pro "before, for, on behalf of, instead of," porro "forward," prae "before;" Old English fore (prep.) "before, in front of;" (adv.) "before, previously;" German vor "for;" Old Church Slavonic pra-dedu "great-grandfather;" Russian pere- "through;" Lithuanian per "through;" Old Irish air- Gothic fair-, German ver-, Old English fer-, intensive prefixes.
per annum: Latin, literally "by the year," from per (see per) + annum, accusative singular of annus "year" (see annual).
per capita: Latin, literally "by the head," from per (see per) + capita "head" (see capital).
per diem: Latin, literally "by the day," from per (see per) + diem, accusative singular of dies "day" (see diurnal). As a noun from 1809.
per se: Latin, literally "by itself;" translating Greek kath auto (Aristotle).
per stirpes: Latin, "by families, by stocks;" in legal use, for inheritances, etc., opposed to per capita.
per-: word-forming element meaning "through, throughout; thoroughly; entirely, utterly," from Latin preposition per (see per (prep.)).
peradventure (adv.): 1620s, from Middle English peraventure (mid-15c.), from per auenture (late 13c.), from Old French par aventure (see adventure). Refashioned as though from Latin.
perambulate (v.): 1560s, from Latin perambulatus, past participle of perambulare "to walk through, go through, ramble through," from per- "through" (see per) + ambulare "to walk" (see amble). Related: Perambulated; perambulating.
perambulation (n.): mid-15c., from Anglo-Latin (c.1300) and Anglo-French perambulacion, from Medieval Latin perambulationem (nominative perambulatio), noun of action from past participle stem of Latin perambulare (see perambulate).
perambulator (n.): 1610s, "one who perambulates," agent noun in Latin form from perambulate. Sense of "baby carriage" is first recorded 1856; often colloquially shortened to pram.