Online Etymology Dictionary

play-list (n.): also playlist, 1975 in the radio station sense, from play (v.) + list (n.).
play-pen (n.): also playpen, 1931, from play + pen (n.2).
play-time (n.): also playtime, 1660s in the recreational sense, from play (n.) + time (n.).
playbook (n.): also play-book, 1530s, "book of stage plays," from play (n.) + book (n.). Meaning "Book of football plays" recorded from 1965.
playboy (n.): 1829, "wealthy bon vivant," from play (v.) + boy. Fem. equivalent playgirl first recorded 1934. As the name of a U.S. based magazine for men, from December 1953.
player (n.): Old English plegere, agent noun from play (v.). Stage sense is from mid-15c. As a pimp's word for himself (also playa), attested from 1974. Player-piano attested from 1901.
playful (adj.): mid-13c., from play (v.) + -ful. Related: Playfully; playfulness.
playground (n.): 1780, from play (v.) + ground (n.). Old English had plegstow "village sports ground," literally "place for play."
playhouse (n.): late Old English pleghus; see play (n.) + house (n.).
playmate (n.): 1640s, "companion, playfellow," from play (v.) + mate (n.). The sexual sense is from 1954 and the launch of "Playboy" magazine.
plaything (n.): 1670s, from play (v.) + thing.
playwright (n.): 1680s, from play (n.) + wright.
plaza (n.): 1830, from Spanish plaza "square, place," from Vulgar Latin *plattia, from Latin platea "courtyard, broad street" (see place (n.)).
plea (n.): early 13c., "lawsuit," from Anglo-French plai (late 12c.), Old French plait "lawsuit, decision, decree" (9c.), from Medieval Latin placitum "lawsuit," in classical Latin, "opinion, decree," literally "that which pleases, thing which is agreed upon," properly neuter past participle of placere (see please). Sense development seems to be from "something pleasant," to "something that pleases both sides," to "something that has been decided." Meaning "a pleading, an agreement in a suit" is attested from late 14c. Plea-bargaining is first attested 1963. Common pleas (early 13c.) originally were legal proceedings over which the Crown did not claim exclusive jurisdiction (as distinct from pleas of the Crown); later "actions brought by one subject against another."
plead (v.): mid-13c., "make a plea in court," from Anglo-French pleder, Old French plaidier, "plead at court" (11c.), from Medieval Latin placitare, from Late Latin placitum (see plea). Sense of "request, beg" first recorded late 14c. Related: Pleaded; pleading; pleadingly.
pleading (n.): late 13c., "the carrying on of a suit at court," verbal noun from plead (v.). Meaning "supplication, intercession" is from early 15c.
pleasance (n.): late 14c., from Old French plaisance "pleasure, delight, enjoyment," from plaisant (see pleasant).
pleasant (adj.): late 14c. (early 14c. as a surname), from Old French plaisant "pleasant, pleasing, agreeable" (12c.), present participle of plaisir "to please" (see please). Pleasantry has the word's modern French sense of "funny, jocular." Related: Pleasantly.
pleasantry (n.): "sprightly humor in conversation," 1650s, from French plaisanterie "joke, jest; joking, jesting," from plaisant (see pleasant). Related: Pleasantries.
please (v.): early 14c., "to be agreeable," from Old French plaisir "to please, give pleasure to, satisfy" (11c., Modern French plaire, the form of which is perhaps due to analogy of faire), from Latin placere "to be acceptable, be liked, be approved," related to placare "to soothe, quiet" (source of Spanish placer, Italian piacere), possibly from PIE *plak-e- "to be calm," via notion of still water, etc., from root *plak- (1) "to be flat" (see placenta).

Meaning "to delight" in English is from late 14c. Inverted use for "to be pleased" is from c.1500, first in Scottish, and paralleling the evolution of synonymous like (v.). Intransitive sense (e.g. do as you please) first recorded c.1500; imperative use (e.g. please do this), first recorded 1620s, was probably a shortening of if it please (you) (late 14c.). Related: Pleased; pleasing; pleasingly.

Verbs for "please" supply the stereotype polite word (e.g. "Please come in," short for may it please you to ...) in many languages (French, Italian), "But more widespread is the use of the first singular of a verb for 'ask, request' " [Buck, who cites German bitte, Polish proszę, etc.]. Spanish favor is short for hace el favor "do the favor." Danish has in this sense vær saa god, literally "be so good."
pleased (adj.): "satisfied, contented," late 14c., past participle adjective from please (v.).
pleaser (n.): 1520s, agent noun from please.
pleasurable (adj.): 1570s, from pleasure (n.) + -able. Related: Pleasurability; pleasurably. For sense, cf. comfortable.
pleasure (n.): late 14c., "condition of enjoyment," from Old French plesir, also plaisir "enjoyment, delight, desire, will" (12c.), from noun use of infinitive plaisir (v.) "to please," from Latin placere "to please, give pleasure, be approved" (see please (v.)). Ending altered in English 14c. by influence of words in -ure (measure, etc.). Meaning "sensual enjoyment as the chief object of life" is attested from 1520s.
pleasure (v.): 1530s, "to take pleasure in;" 1550s as "give pleasure to," from pleasure (n.). Sexual sense by 1610s. Related: Pleasured; pleasuring.
pleasure-seeker (n.): from pleasure (n.) + agent noun from seek.
pleat (v.): 1560s, used as the verb version of plait (n.) and probably representing an alternative pronunciation. Related: Pleated; pleating.
pleat (n.): "a fold," 1580s, variant of plait (n.). With a gap in the printed record 17c.-18c., but probably it was in continuous oral use.
pleather (n.): by 1991, from plastic + leather.
pleb (n.): 1856 as a colloquial shortening of plebeian in the ancient Roman sense. West Point sense attested by 1851 (see plebe).
plebe (n.): also pleb, "member of the lowest class at a U.S. military academy," 1833, probably a shortened form of plebeian "one of the lower class," which in Latin also had the short form plebs or plebes.
plebeian (n.): "member of the lowest class," 1530s, from Latin plebius "person not of noble rank," from adjective meaning "of the common people" (see plebeian (adj.)).
plebeian (adj.): also plebian, "of or characteristic of the lower class," 1560s in a Roman historical sense, from Latin plebeius "belonging to the plebs," earlier plebes, "the populace, the common people" (as opposed to patricians, etc.), also "commonality; the mass, the multitude; the lower class," from PIE *ple- (see pleio-). In general (non-historical) use from 1580s.
plebiscite (n.): "direct vote of the people," 1860 (originally in reference to Italian unification), from French plébiscite (1776 in modern sense, originally with reference to Switzerland), from Latin plebiscitum "a decree or resolution of the people," from plebs (genitive plebis) "the common people" (see plebeian (adj.)) + scitum "decree," noun use of neuter past participle of sciscere "to assent, vote for, approve," inchoative of scire "to know" (see science). Used earlier (1530s) in a purely Roman historical context. Related: Plebiscitary.
plectrum (n.): something used to pluck the strings of a musical instrument, 1620s, from Latin plectrum, from Greek plektron "thing to strike with" (pick for a lyre, cock's spur, spear point, etc.), from plek-, root of plessein "to strike" (see plague (n.)).
pled: past tense and past participle of plead (v.).
pledge (v.): c.1400, "to promise" (something to someone), "to give over as security for repayment," also "promise faith to," from pledge (n.) and from Old French plegier, from plege (n.). From mid-15c. as "to stand surety for, be responsible for;" late 15c. as "to mortgage." Meaning "put (someone) under oath" is from 1570s; sense of "to solemnly promise or guarantee" is from 1590s, as is sense "to drink a toast." Related: Pledged; pledging.
pledge (n.): mid-14c., "surety, bail," from Old French plege (Modern French pleige) "hostage, security, bail," probably from Frankish *plegan "to guarantee," from *pleg-, a West Germanic root meaning "have responsibility for" (cf. Old Saxon plegan "vouch for," Middle Dutch plien "to answer for, guarantee," Old High German pflegan "to care for, be accustomed to," Old English pleon "to risk the loss of, expose to danger;" see plight (v.)).

Meaning "allegiance vow attested by drinking with another" is from 1630s. Sense of "solemn promise" first recorded 1814, though this notion is from 16c. in the verb. Weekley notes the "curious contradiction" in pledge (v.) "to toast with a drink" (1540s) and pledge (n.) "the vow to abstain from drinking" (1833). Meaning "student who has agreed to join a fraternity or sorority" dates from 1901.
Pleiades (n.): late 14c., the seven daughters of Atlas and Pleione, transformed by Zeus into seven stars, from Latin Pleiades, from Greek Pleiades, perhaps literally "constellation of the doves" from a shortened form of peleiades, plural of peleias "dove" (from PIE root *pel- "dark-colored, gray"). Or perhaps from plein "to sail," because the season of navigation begins with their heliacal rising.

Old English had the name from Latin as Pliade. Mentioned by Hesiod (pre-700 B.C.E.), only six now are visible to most people; on a clear night a good eye can see nine (in 1579, well before the invention of the telescope, the German astronomer Michael Moestlin (1550-1631) correctly drew 11 Pleiades stars); telescopes reveal at least 500. Hence French pleiade, used for a meeting or grouping of seven persons.
plein-air (adj.): 1894, from French phrase en plein air, literally "in the open air." The style developed among French impressionists c.1870.
pleio-: also pleo-, word-forming element meaning "more," from comb. form of Greek pleion "larger, greater in quantity, the more part, very many" (comp. of polys "much"), from PIE *ple- (cf. Latin plere "to fill," plebes, "the populace, the common people;" Greek plethein "be full," pleres "full"), possibly a variant of *pele- (1) "to fill" (see poly-).
pleiotropy (n.): 1921, from German pleiotrop (1910), from Greek pleion "greater in quantity, the more part, very many," (see pleio-) + trope "turn, turning" (see trope). Related: Pleiotropic; pleiotropism.
Pleistocene (adj.): "pertaining to the glacial period," 1839, coined by Lyell from Greek pleistos "most" (superlative of polys "much;" see poly-) + -cene.
plenary (adj.): 1510s, earlier plenar (mid-13c.), from Old French plenier, from Medieval Latin plenarius "entire, complete," from Latin plenus "full, filled, greatly crowded; stout, pregnant; abundant, abounding; complete," from PIE *pele- (1) "to fill" (see poly-). Related: Plenarily.
plenipotentiary (adj.): 1640s, from French plénipotentiaire and directly from Medieval Latin plenipotentiarius "having full power," from Late Latin plenipotens, from Latin plenus "full" (see plenary) + potentem "powerful" (see potent). As a noun from 1650s.
plenitude (n.): early 15c., from Old French plenitude and directly from Latin plenitudinem (nominative plenitudo) "abundance, completeness, fullness," from plenus "complete, full" (see plenary).
plenteous (adj.): c.1300, plentivous, from Old French plentiveus "fertile, rich" (early 13c.), from plentif "abundant," from plentee "abundance" (see plenty). Related: Plentifully; plentifulness.
plentiful (adj.): late 15c., from plenty + -ful. Related: Plentifully.
plentitude (n.): 1610s, erroneous form of plenitude.
plenty (n.): mid-13c., "as much as one could desire," from Old French plentee, earlier plentet "abundance, profusion" (12c., Modern French dialectal plenté), from Latin plenitatem (nominative plenitas) "fullness," from plenus "complete, full" (see plenary). Meaning "condition of general abundance" is from late 14c. The colloquial adverb meaning "very much" is first attested 1842. Middle English had parallel formation plenteth, from the older Old French form of the word.