plague (v.) Look up plague at Dictionary.com
late 15c., from Middle Dutch plaghen, from plaghe (n.) "plague" (see plague (n.)). Sense of "bother, annoy" it is first recorded 1590s. Related: Plagued; plaguing.
plaguey (adj.) Look up plaguey at Dictionary.com
1570s, "pertaining to a plague," from plague (n.) + -y (2). Figurative meaning "vexatious" is from 1610s. As an adverb (properly it would be plaguily) it is attested from 1580s, often with deliberate attempt at humor.
plaice (n.) Look up plaice at Dictionary.com
type of European edible flatfish, late 13c., from Old French plaise (12c., Modern French plie), from Late Latin platessa "plaice, flatfish," perhaps related to or from Greek platys "broad, flat," from PIE *plat- "to spread" (cognates: Sanskrit prathati "spreads out;" Hittite palhi "broad;" Lithuanian platus "broad;" German Fladen "flat cake;" Old Norse flatr "flat;" Old English flet "floor, dwelling;" Old Irish lethan "broad"); extended variant form of root *pele- (2) "flat; to spread" (see plane (n.1)).
plaid (n.) Look up plaid at Dictionary.com
1510s, from Scottish, from or related to Gaelic plaide "blanket, mantle," of unknown origin, perhaps a contraction of peallaid "sheepskin," from peall "skin," from Latin pellis (but OED finds this "phonetically improbable"). The wearing of it by males forbidden by act of parliament, under penalty of transportation, 1746-82. As an adjective c.1600, from the noun.
plain (adj.) Look up plain at Dictionary.com
c.1300, "flat, smooth," from Old French plain "flat, smooth, even" (12c.), from Latin planus "flat, even, level" (see plane (n.1)). Sense of "evident" is from, c.1300; that of "free from obstruction" is early 14c.; meaning "simple, sincere, ordinary" is recorded from late 14c., especially of dress, "unembellished, without decoration."

In reference to the dress and speech of Quakers, it is recorded from 1824; of Amish and Mennonites, from 1894 (in the Dutch regions of Pennsylvania Plain with the capital is shorthand adjective for "Amish and Old Order Mennonite"). Of appearance, as a euphemism for "ill-favored, ugly" it dates from 1749. Of envelopes from 1913. As an adverb from early 14c. Plain English is from c.1500. Plain dealer "one who deals plainly or speaks candidly" is from 1570s, marked "Now rare" in OED 2nd edition. To be as plain as the nose on (one's) face is from 1690s.
plain (n.) Look up plain at Dictionary.com
"level country," c.1300 (in reference to Salisbury Plain), from Old French plain "open countryside," from Latin planum "level ground, plain," noun use of neuter of planus (adj.) "flat, even, level" (see plane (n.1)). Latin planum was used for "level ground" but much more common was campus.
plain clothes (n.) Look up plain clothes at Dictionary.com
"ordinary dress" (as opposed to military uniform), 1822; of police detectives, it is attested from 1842. Also plainclothes.
plain Jane Look up plain Jane at Dictionary.com
"unattractive woman," first attested 1912.
plain-song (n.) Look up plain-song at Dictionary.com
also plainsong, plain-song, 1510s, translating Latin cantus planus, French plain chant.
plain-spoken (adj.) Look up plain-spoken at Dictionary.com
1670s, from plain (adj.) + spoken.
plainly (adv.) Look up plainly at Dictionary.com
late 14c., from plain (adj.) + -ly (2). Meaning "simply, frugally" is from 1560s.
plainness (n.) Look up plainness at Dictionary.com
c.1300, "flatness," from plain (adj.) + -ness. Meaning "clarity" is mid-15c.; that of "open conduct" is from 1540s; that of "absence of ornament" is from 1580s.
plains (n.) Look up plains at Dictionary.com
of the American Midwest, 1755 (in singular form from 1680s), see plain (n.). Plains Indian attested from 1844.
plainsman (n.) Look up plainsman at Dictionary.com
1858, from plains + man (n.).
plaint (n.) Look up plaint at Dictionary.com
"expression of sorrow," c.1200, from Old French plainte "lament, lamentation" (12c.), from Latin planctus "lamentation, wailing, beating of the breast," from past participle stem of plangere "to lament, to strike" (see plague (n.)). Connecting notion probably is beating one's breast in grief.
plaintiff (n.) Look up plaintiff at Dictionary.com
c.1400, from Anglo-French pleintif (late 13c.), noun use of Old French plaintif "complaining; wretched, miserable," from plainte (see plaint). Identical with plaintive at first; the form that receded into legal usage retained the older -iff spelling.
plaintive (adj.) Look up plaintive at Dictionary.com
late 14c., "lamenting," from Old French plaintif "complaining; wretched, miserable," from plainte (see plaint). Sense of "mournful, sad" first recorded 1570s. Related: Plaintively; plaintiveness.
plait (v.) Look up plait at Dictionary.com
late 14c., "to fold, gather in pleats," also "to braid or weave," from Old French pleir "to fold," variant of ploier, ployer "to fold, bend," from Latin plicare "to fold" (see ply (v.1)). Related: Plaited; plaiting.
plait (n.) Look up plait at Dictionary.com
c.1400, "a fold, a crease," from Anglo-French pleit, Old French ploit, earlier pleit, "fold, manner of folding," from Latin plicatus, past participle of plicare "to lay, fold, twist" (see ply (v.1)). Meaning "interlaced strands of hair, ribbon, etc." is from 1520s, perhaps from plait (v.).
plan (n.) Look up plan at Dictionary.com
1670s as a technical term in perspective drawing; 1706 as "drawing, sketch, or diagram of any object," from French plan "ground plan, map," literally "plane surface" (mid-16c.), from Latin planum "level or flat surface," noun use of adjective planus "level, flat" (see plane (n.1)). The notion is of "a drawing on a flat surface." Meaning "scheme of action, design" is first recorded 1706, possibly influenced by French planter "to plant," from Italian planta "ground plan."
plan (v.) Look up plan at Dictionary.com
1728, "make a plan of," from plan (n.). Related: Planned; planning; plans. Planned economy is attested from 1931. Planned Parenthood (1942) formerly was Birth Control Federation of America.
planar (adj.) Look up planar at Dictionary.com
1850, from Latin planaris "level, flat," from planum "plane" (see plane (n.1)).
Planaria (n.) Look up Planaria at Dictionary.com
flat worm-like animal, 1819, from Modern Latin (1776) noun use of fem. of Latin planarius, literally "on level ground" (here used to mean "flat"), from planum, planus "flat, level, even, plain" (see plane (n.1)). Related: Planarian.
planchet (n.) Look up planchet at Dictionary.com
"metal disk out of which a coin is made," 1610s, from French planchette, literally "a small board," diminutive of Old French planche (12c.), from Latin planca "board, slab, plank" (see plank). The planchette used in automatism and on Ouija boards is a re-borrowing of the French word, 1860.
Planck Look up Planck at Dictionary.com
in physics, in reference to the work of German physicist Max Planck (1858-1947); such as Planck's constant, attested in English from 1901.
plane (n.1) Look up plane at Dictionary.com
"flat surface," c.1600, from Latin planum "flat surface, plane, level, plain," noun use of neuter of adjective planus "flat, level, even, plain, clear," from PIE *pla-no- (cognates: Lithuanian plonas "thin;" Celtic *lanon "plain;" perhaps also Greek pelanos "sacrificial cake, a mixture offered to the gods, offering (of meal, honey, and oil) poured or spread"), suffixed form of root *pele- (2) "to spread out, broad, flat" (cognates: Old Church Slavonic polje "flat land, field," Russian polyi "open;" Old English and Old High German feld, Middle Dutch veld "field"). Introduced (perhaps by influence of French plan in this sense) to differentiate the geometrical senses from plain, which in mid-16c. English also meant "geonetric plane." Figurative sense is attested from 1850. As an adjective from 1660s.
plane (n.2) Look up plane at Dictionary.com
1908, short for aeroplane (see airplane).
plane (n.3) Look up plane at Dictionary.com
"tool for smoothing surfaces," mid-14c., from Old French plane, earlier plaine (14c.), from Late Latin plana, back-formation from planare "make level," from Latin planus "level, flat" (see plane (n.1)).
plane (v.2) Look up plane at Dictionary.com
"soar, glide on motionless wings," early 15c., from Old French planer "to hover (as a bird), to lie flat," from plan (n.) "plane," from Latin planum "flat surface" (see plane (n.1)), on notion of bird gliding with flattened wings. Of boats, etc., "to skim over the surface of water," it is first found 1913. Related: Planed; planing.
plane (n.4) Look up plane at Dictionary.com
"tree of the genus Platanus," late 14c., from Old French plane, earlier plasne (14c.), from Latin platanus, from Greek platanos, earlier platanistos "plane tree," a species from Asia Minor, associated with platys "broad" (see plaice (n.)), in reference to its leaves. Applied since 1778 in Scotland and northern England to the sycamore, whose leaves somewhat resemble those of the true plane tree.
plane (v.1) Look up plane at Dictionary.com
"to make smooth," early 14c., "to gloss over, explain away;" mid-14c. as "to make smooth or even," from Old French planer "to smooth, level off; wipe away, erase" (12c.), from Late Latin planare "make level," from Latin planus "level, flat" (see plane (n.1)). In early use in English often plain. Related: Planed; planing.
planet (n.) Look up planet at Dictionary.com
late Old English planete, from Old French planete (Modern French planète), from Late Latin planeta, from Greek planetes, from (asteres) planetai "wandering (stars)," from planasthai "to wander," of unknown origin, possibly from PIE *pele- (2) "flat, to spread" on notion of "spread out." So called because they have apparent motion, unlike the "fixed" stars. Originally including also the moon and sun; modern scientific sense of "world that orbits a star" is from 1630s.
planetarium (n.) Look up planetarium at Dictionary.com
1734, "orrery," Modern Latin, from Late Latin planeta (see planet) + Latin -arium "a place for." Sense of "device for projecting the night sky onto the interior of a dome" is attested from 1929.
planetary (adj.) Look up planetary at Dictionary.com
1590s; see planet + -ary. Probably from Late Latin planetarius "pertaining to a planet or planets," but this is attested only as "an astrologer." Planetary nebula, so called for its shape, attested from 1785.
plangent (adj.) Look up plangent at Dictionary.com
"beating with a loud sound," 1822, from Latin plangentem (nominative plangens), present participle of plangere "to strike, beat" (see plague (n.)). Related: Plangently.
plani- Look up plani- at Dictionary.com
word-forming element meaning "level, plane," from Latin plani-, from planus "flat, level" (see plane (n.1)).
planisphere (n.) Look up planisphere at Dictionary.com
late 14c., from Medieval Latin planisphaerium, from Latin planus (see plane (n.1)) + sphaera (see sphere (n.)).
plank (n.) Look up plank at Dictionary.com
late 13c. (c.1200 as a surname), from Old North French planke, variant of Old French planche "plank, slab, little wooden bridge" (12c.), from Late Latin planca "broad slab, board," probably from Latin plancus "flat, flat-footed," from PIE *plak- (1) "to be flat" (see placenta). Technically, timber sawed to measure 2 to 6 inches thick, 9 inches or more wide, and 8 feet or more long. Political sense of "item of a party platform" is U.S. coinage from 1848. To walk the plank, supposedly a pirate punishment, is first attested 1789 and most early references are to slave-traders disposing of excess human cargo in crossing the ocean.
planktology (n.) Look up planktology at Dictionary.com
1892, from German planktologie (1891); see plankton + -logy. The native formation planktonology (1896) is less common.
plankton (n.) Look up plankton at Dictionary.com
1891, from German Plankton (1887), coined by German physiologist Viktor Hensen (1835-1924) from Greek plankton, neuter of planktos "wandering, drifting," verbal adjective from plazesthai "to wander, drift," from plazein "to drive astray," from PIE root *plak- (2) "to strike, hit" (see plague (n.)). Related: Planktonic.
planner (n.) Look up planner at Dictionary.com
1716, "one who plans," agent noun from plan (v.). Derogatory variant planster attested from 1945. Meaning "book or device that enables one to plan" is from 1971.
planning (n.) Look up planning at Dictionary.com
1748, verbal noun from plan (v.).
plano- Look up plano- at Dictionary.com
alternative form of Latin plani- "flat, level," but also used in sciences as a comb. form of Greek planos "wandering" (see planet).
plant (n.) Look up plant at Dictionary.com
Old English plante "young tree or shrub, herb newly planted," from Latin planta "sprout, shoot, cutting" (source of Spanish planta, French plante), perhaps from *plantare "to drive in with the feet, push into the ground with the feet," from planta "sole of the foot," from nasalized form of PIE *plat- "to spread, flat" (see place (n.)).

Broader sense of "any vegetable life, vegetation generally" is first recorded 1550s. Most extended usages are from the verb, on the notion of "something planted;" such as "construction for an industrial process," 1789, at first with reference to the set-up of machinery, later also the building; also slang meaning "a spy" (1812). Many of these follow similar developments in the French form of the word. German Pflanz, Irish cland, Welsh plant are from Latin.
plant (v.) Look up plant at Dictionary.com
"put in the ground to grow," Old English plantian, from Latin plantare (see plant (n.)). Reinforced by cognate Old French planter. Without reference to growing, "to insert firmly," late 14c. Of colonies from c.1300. Figuratively, of ideas, etc., from early 15c. Meaning "to bury" is U.S. slang from U.S., 1855. Related: Planted; planting.
plantain (n.1) Look up plantain at Dictionary.com
"banana," 1550s, plantan, from Spanish plátano, plántano, probably from Carib palatana "banana" (Arawak pratane), and altered by association with Spanish plátano "plane tree," from Medieval Latin plantanus "plane tree," itself altered (by association with Latin planta "plant") from Latin platanus (see plane (n.4)). So called from the shape of its leaves. There is no similarity or relation between this plant and plantain (n.2).
plantain (n.2) Look up plantain at Dictionary.com
"weed of the genus Plantago," mid-13c., from Anglo-French plaunteyne, Old French plantain, from Latin plantaginem (nominative plantago), the common weed, from planta "sole of the foot" (see plant (n.)); so called from its flat leaves.
plantar (adj.) Look up plantar at Dictionary.com
1706, from Latin plantaris "pertaining to the sole of the foot," from planta "sole of the foot" (see plant (n.)).
plantation (n.) Look up plantation at Dictionary.com
mid-15c., "action of planting," from Middle French plantation, from Latin plantationem (nominative plantatio) "a planting," noun of action from past participle stem of plantare "to plant" (see plant). Historically used for "colony, settlement in a new land" (1610s); meaning "large farm on which tobacco or cotton is grown" is first recorded 1706.
planter (n.) Look up planter at Dictionary.com
"one who sows seeds," late 14c., agent noun from plant (v.). Mechanical sense by 1850. Meaning "proprietor of a cultivated estate in West Indies or southern colonies of North America" is from 1640s, hence planter's punch (1924). Meaning "a pot for growing plants" recorded by 1959.