Online Etymology Dictionary

plight (v.): "to pledge" (obsolete except in archaic plight one's troth), from Old English pligtan, plihtan "to endanger, imperil, compromise," verb form of pliht (n.) "danger, risk," from PIE root *dlegh- "to engage oneself," forming words in Celtic, Germanic, Slavic, and possibly Latin (see play (v.)). Related: Plighted; plighting.
plight (n.1): "condition or state (usually bad)," late 12c., "danger, harm, strife," from Anglo-French plit, pleit, Old French pleit, ploit "condition" (13c.), originally "way of folding," from Vulgar Latin *plictum, from Latin plicitum, neuter past participle of Latin plicare "to fold, lay" (see ply (v.1)).

Originally in neutral sense (as in modern French en bon plit "in good condition"), sense of "harmful state" (and current spelling) probably is from convergence and confusion with plight (n.2) via notion of "entangling risk, pledge or promise with great risk to the pledger."
plight (n.2): "pledge," mid-13c., "pledge, promise," usually involving risk or loss in default, from Old English pliht "danger, risk, peril, damage," from Proto-Germanic *pleg- (source also of Old Frisian plicht "danger, concern, care," Middle Dutch, Dutch plicht "obligation, duty," Old High German pfliht, German Pflicht "obligation, duty" (see plight (v.)). Compare Old English plihtere "look-out man at the prow of a ship," plihtlic "perilous, dangerous."
Plimsoll (n.): "mark on the hull of a British ship showing how deeply she may be loaded," 1881, from Samuel Plimsoll (1824-1898), M.P. for Derby and advocate of shipping reforms (which were embodied in the Merchant Shipping Act of 1876). Sense extended 1907 to "rubber-soled canvas shoe" (equivalent of American English sneakers) because the band around the shoes that holds the two parts together reminded people of a ship's Plimsoll line; sense perhaps reinforced by sound association with sole (which sometimes influenced the spelling to plimsole). The name is of Huguenot origin.
plink (v.): 1941, imitative. As a noun from 1954. Related: Plinked; plinking.
plinth (n.): 1610s, from French plinthe (16c.) and directly from Latin plinthus, from Greek plinthos "brick, squared stone," cognate with Old English flint (see flint).
plio-: word-forming element, Latinate form of pleio-.
Pliocene (adj.): 1833, from plio- "more" (Latinized form of pleio-) + -cene.
PLO: initialism (acronym) of Palestinian Liberation Organization, by 1965.
plod (v.): 1560s, of uncertain origin, perhaps imitative of the sound of walking heavily or slowly. Related: Plodded; plodding.
plodding (adj.): "diligent and dull," 1580s, present participle adjective from plod (v.).
plonk (v.): 1874, imitative. From 1903 as a noun. Related: Plonked; plonking.
plop (v.): 1821, imitative of the sound of a smooth object dropping into water. Related: Plopped; plopping. Thackary (mid-19c.) used plap (v.). As a noun from 1833.
plosive (n.): type of consonantal sound, 1899, from explosive. As an adjective from 1909.
plot (n.): Old English plot "small piece of ground," of unknown origin. Sense of "ground plan," and thus "map, chart" is 1550s; that of "a secret, plan, scheme" is 1580s, probably by accidental similarity to complot, from Old French complot "combined plan," of unknown origin, perhaps a back-formation from compeloter "to roll into a ball," from pelote "ball." Meaning "set of events in a story" is from 1640s. Plot-line (n.) attested from 1957.
plot (v.): 1580s, "to lay plans for" (usually with evil intent); 1590s in the literal sense of "to make a map or diagram," from plot (n.). Related: Plotted; plotter; plotting.
plough: alternative spelling of plow. Related: Ploughed; ploughing.
plover (n.): c. 1300, from Anglo-French plover, Old French pluvier, earlier plovier (c. 1200), from Vulgar Latin *plovarius, literally "belonging to rain," from Latin pluvia "rain (water)" from pluere "to rain," from PIE root *pleu- "to flow" (see pluvial). Perhaps so called because the birds' migration arrival coincides with the start of the rainy season, or from its supposed restlessness when rain approaches.
plow (n.): late Old English plog, ploh "plow; plowland" (a measure of land equal to what a yoke of oxen could plow in a day), possibly from a Scandinavian source (such as Old Norse plogr "plow," Swedish and Danish plog), from Proto-Germanic *plogo- (source also of Old Saxon plog, Old Frisian ploch "plow," Middle Low German ploch, Middle Dutch ploech, Dutch ploeg, Old High German pfluog, German Pflug), a late word in Germanic, of uncertain origin. Old Church Slavonic plugu, Lithuanian plugas "plow" are Germanic loan-words, as probably is Latin plovus, plovum "plow," a word said by Pliny to be of Rhaetian origin.

Replaced Old English sulh, cognate with Latin sulcus "furrow" (see sulcus). As a name for the star pattern also known as the Big Dipper or Charles's Wain, it is attested by early 15c., perhaps early 14c. The three "handle" stars (in the Dipper configuration) generally are seen as the team of oxen pulling the plow, though sometimes they are the handle.
plow (v.): late 14c., from plow (n.). Transferred sense from 1580s. Related: Plowed; plowing.
plow-boy (n.): also plowboy, 1560s, from plow + boy.
plowman (n.): also plow-man, c. 1300, from plow + man (n.).
plowshare (n.): late 14c., from plow + share (n.2). To beat swords into plowshares is from Isaiah ii:4.
ploy (n.): 1722, "anything with which one amuses oneself," Scottish and northern England dialect, possibly a shortened form of employ or deploy. Popularized in the sense "move or gambit made to gain advantage" by British humorist Stephen Potter (1900-1969).
pluck (v.): late Old English ploccian, pluccian "pull off, cull," from West Germanic *plokken (source also of Middle Low German plucken, Middle Dutch plocken, Dutch plukken, Flemish plokken, German pflücken), perhaps from Vulgar Latin *piluccare (source of Old French peluchier, late 12c.; Italian piluccare), a frequentative, ultimately from Latin pilare "pull out hair," from pilus "hair" (see pile (n.3)). But despite the similarities, OED finds difficulties with this and cites gaps in historical evidence. Related: Plucked; plucking.
To pluck a rose, an expression said to be used by women for going to the necessary house, which in the country usually stands in the garden. [F. Grose, "Classical Dictionary of the Vulgar Tongue," 1785]
This euphemistic use is attested from 1610s. To pluck up "summon up" is from c. 1300.
pluck (n.): c. 1400, "act of plucking," from pluck (v.). Meaning "courage, boldness" (1785), originally in pugilism slang, is a figurative use from earlier meaning "heart, viscera" (1610s) as that which is "plucked" from slaughtered livestock. Perhaps influenced by figurative use of the verb in pluck up (one's courage, etc.), attested from c. 1300.
plucky (adj.): 1831, from pluck (n.) + -y (2). Related: Pluckily; pluckiness.
plug (n.): 1620s, originally a seamen's term, probably from Dutch plug, Middle Dutch plugge "bung, stopper," related to Norwegian plugg, Danish pløg, North Frisian plaak, Middle Low German pluck, German Pflock; further etymology uncertain. Irish and Gaelic words are from English. Sense of "wad or stick of tobacco" is attested from 1728, based on resemblance. Electrical sense is from 1883, based on being inserted; meaning "sparking device in an internal combustion engine" is from 1886. Meaning "advertisement" first recorded 1902, American English, perhaps from verb sense "work energetically at" (c. 1865).
plug (v.): "close tightly (a hole), fill," 1620s, from plug (n.) or from Dutch pluggen. Meaning "work energetically at" is c. 1865. Sense of "popularize by repetition" is from 1906. Slang sense "put a bullet into" is recorded from 1870. Related: Plugged; plugging.
plug-in (adj.): 1922, from plug (v.) + in (adv.).
plug-ugly (n.): "ruffian," 1856, originally in Baltimore, Maryland, from plug (n.), American English slang name for the stovepipe hats then popular among young men, + ugly.
plugger (n.): 1867, agent noun from plug (v.).
plum (n.): Old English plume "plum, plum tree," from an early Germanic borrowing (Middle Dutch prume, Dutch pruim, Old High German pfluma, pfruma, German Pflaume) from Vulgar Latin *pruna, from Latin prunum "plum," from Greek prounon, later form of proumnon, of unknown origin, perhaps from an Asiatic language (Phrygian?). Also see prune (n.). Change of pr- to pl- is peculiar to Germanic. The vowel shortened in early modern English. Meaning "something desirable" is first recorded 1780, probably in reference to the sugar-rich bits of a plum pudding, etc.
plumage (n.): late 14c., "feathers," from Old French plumage "plumage, appearance" (14c.), from plume (see plume (n.)).
plumassier (n.): "dealer in ornamental feathers," from French plumassier, from Middle French plumasse "plume of feather," from plume (see plume).
plumb (n.): "lead hung on a string to show the vertical line," early 14c., from Old French *plombe, plomee "sounding lead," and directly from Late Latin *plumba, originally plural of Latin plumbum "lead (the metal), lead ball; pipe; pencil," a word of unknown origin, related to Greek molybdos "lead" (dialectal bolimos) and perhaps from an extinct Mediterranean language, perhaps Iberian.
plumb (v.): early 15c., "to sink" (like lead), from plumb (n.). Meaning "take soundings with a plumb" is first recorded 1560s; figurative sense of "to get to the bottom of" is from 1590s. Related: Plumbed; plumbing.
plumb (adj.): "perpendicular, vertical," mid-15c., from plumb (n.). The notion of "exact measurement" led to extended sense of "completely, downright" (1748), sometimes spelled plump, plum, or plunk.
plumb-bob (n.): 1835, from plumb (n.) + bob (n.1).
plumbago (n.): "graphite," 1784, from Latin plumbago "a type of lead ore, black lead," from plumbum "lead" (see plumb (n.)); it renders Greek molybdaina, which was used of yellow lead oxide and also of a type of plant (leadwort). Attested in English in the yellow oxide sense from 1610s; as a type of plant from 1747. Related: Plumbaginous.
plumber (n.): late 14c. (from c. 1100 as a surname), "a worker in any sort of lead" (roofs, gutters, pipes), from Old French plomier "lead-smelter" (Modern French plombier) and directly from Latin plumbarius "worker in lead," noun use of adjective meaning "pertaining to lead," from plumbum "lead" (see plumb (n.)). Meaning focused 19c. on "workman who installs pipes and fittings" as lead water pipes became the principal concern of the trade. In U.S. Nixon administration (1969-74), the name of a special unit for investigation of "leaks" of government secrets.
plumbic (adj.): "combined with lead," 1799, from Latin plumbum (see plumb (n.)) + -ic.
plumbing (n.): mid-15c., "the weighting of a fishing line," verbal noun from plumb (v.). Specific meaning "water and drainage pipes" is recorded by 1875, American English.
THE apparatus by which the water from a reservoir is carried about over a building and delivered at points convenient for use, is called by the general name of plumbing. The word "plumbing" means lead-work; and it is used to signify this water apparatus of a house because the pipes of which it largely consists are usually made of lead. [Edward Abbott, "Long Look House: A Book for Boys and Girls," Boston, 1877]
Alternative plumbery also is mid-15c. Slang meaning "a person's reproductive organs" attested by 1975.
plumbo-: word-forming element meaning "lead" (the metal), from comb. form of Latin plumbum "lead" (see plumb (n.)).
plumbous (adj.): 1680s, "leaden;" 1854 in chemistry sense, "containing lead" (especially in a low valence), from Latin plumbosus "full of lead," from plumbum (see plumb (n.)).
plume (n.): late 14c., "a feather" (especially a large and conspicuous one), from Old French plume "soft feather, down; feather bed," and directly from Latin pluma "a feather, down; the first beard," from PIE root *pleus- "to pluck; a feather, fleece" (source of Old English fleos "fleece"). Meaning "a long streamer of smoke, etc." is first attested 1878.
plume (v.): late 14c., "to pluck, strip," from plume (n.). From mid-15c. as "to adorn with plumes." Meaning "to dress the feathers" is from 1702. Related: Plumed; pluming.
plumed (adj.): "adorned with plumes," 1520s, past participle adjective from plume (v.).
plummet (n.): late 14c., "ball of lead, plumb of a bob-line," from Old French plomet "graphite, lead; plummet, sounding lead," diminutive of plom "sounding lead" (see plumb (n.)).
plummet (v.): 1620s, "to fathom, take soundings," from plummet (n.). Meaning "to fall rapidly" first recorded 1933, perhaps originally among aviators. Related: Plummeted; plummeting.