redhead (n.) Look up redhead at Dictionary.com
mid-13c., from red (adj.1) + head (n.). Red (adj.), of persons, "having red hair" is from late Old English.
The Carrot pate be sure you hate, for she'l be true to no man,
But put her too 't and she will do 't, and oft turns very common:
She that is red upon the head will doubtless ne'r forsake it,
But wanton be, assuredly, and willingly will take it.
["The True Lover's Admonition," Roxburghe Ballads, c.1680]
redial (v.) Look up redial at Dictionary.com
also re-dial, 1961, from re- + dial (v.). Related: Redialed; redialing.
redingote (n.) Look up redingote at Dictionary.com
"double-breasted outer coat with long plain skirts," also a similar garment for women, 1793, from French redingote (1725) from English riding coat (c.1500).
redirect (v.) Look up redirect at Dictionary.com
1805 (implied in redirected), from re- "back, again" + direct (v.). Related: Redirecting.
rediscover (v.) Look up rediscover at Dictionary.com
1752, from re- + discover (v.). Related: Rediscovered; rediscovering.
rediscovery (n.) Look up rediscovery at Dictionary.com
1747, from re- + discovery.
redistribute (v.) Look up redistribute at Dictionary.com
1610s, from re- "back, again" + distribute. Related: Redistributed; redistributing.
redistribution (n.) Look up redistribution at Dictionary.com
1831, from French redistribution; see re- + distribution.
redistributive (adj.) Look up redistributive at Dictionary.com
1860, from redistribute + -ive. Related: Redistributively.
redistrict (v.) Look up redistrict at Dictionary.com
"redraw the boundaries of districts," 1838, in U.S. political sense, from re- "again" + district. Related: Redistricted; redistricting.
redivide (v.) Look up redivide at Dictionary.com
c.1600, from re- + divide (v.). Related: Redivided; redividing.
redline (v.) Look up redline at Dictionary.com
also red-line, "mark in red ink," 1820, from red (adj.1) + line (v.). Specific sense of "deny loans to certain neighborhoods based on ethnicity" is from 1973, on notion of lines drawn on maps. Used earlier in reference to insurance company practices (1961) and in World War II military slang in reference to a red line drawn through a soldier's name for some infraction, thus denying his pay. Related: Redlined; redlining.
redneck (n.) Look up redneck at Dictionary.com
"cracker," attested 1830 in a specialized sense ("This may be ascribed to the Red Necks, a name bestowed upon the Presbyterians in Fayetteville" -- Ann Royall, "Southern Tour I," p.148), from red (adj.1) + neck (n.). According to various theories, red perhaps from anger, or from pellagra, but most likely from mule farmers' outdoors labor in the sun, wearing a shirt and straw hat, with the neck exposed. Compare redshanks, old derogatory name for Scots Highlanders and Celtic Irish (1540s), from their going bare-legged.

It turns up again in an American context in 1904, again from Fayetteville, in a list of dialect words, meaning this time "an uncouth countryman" ["Dialect Notes," American Dialect Society, Vol. II, Part VI, 1904], but seems not to have been in widespread use in the U.S. before c.1915. In the meantime, it was used from c.1894 in South Africa (translating Dutch Roinek) as an insulting Boer name for "an Englishman."
Another common Boer name for an Englishman is "redneck," drawn from the fact that the back of an Englishman's neck is often burnt red by the sun. This does not happen to the Boer, who always wears a broad-brimmed hat. [James Bryce, "Impressions of South Africa," London, 1899]
redness (n.) Look up redness at Dictionary.com
Old English readnes; see from red (adj.1) + -ness.
redo (v.) Look up redo at Dictionary.com
also re-do, 1590s, from re- "back, again" + do (v.). Related: Redone; redoing.
redolence (n.) Look up redolence at Dictionary.com
early 15c., from Old French redolence, related to redolent (see redolent).
redolent (adj.) Look up redolent at Dictionary.com
c.1400, from Old French redolent "emitting an odor" and directly from Latin redolentem (moninative redolens), present participle of redolere "emit a scent, diffuse odor," from red-, intensive prefix (see re-), + olere "give off a smell" (see odor).
redouble (v.) Look up redouble at Dictionary.com
mid-15c., "double again, multiply" (trans.), from Middle French redoubler, from Old French re- "again" (see re-) + doubler "to double" (see double (v.)). Meaning "become twice as much" (intrans.) is from late 15c. Related: Redoubled; redoubling.
redoubt (n.) Look up redoubt at Dictionary.com
also redout, "small, enclosed military work," c.1600, from French redoute (17c.), from Italian ridotto, earlier ridotta, "place of retreat," from Medieval Latin reductus "place of refuge, retreat," noun use of past participle of reducere "to lead or bring back" (see reduce). The -b- was added by influence of unrelated English redoubt (v.) "to dread, fear" (see redoubtable). As an adjective, Latin reductus meant "withdrawn, retired; remote, distant."
redoubtable (adj.) Look up redoubtable at Dictionary.com
late 14c., from Old French redoutable (12c.), from redouter "to dread," from re-, intensive prefix, + douter "be afraid of" (see doubt (v.)).
redound (v.) Look up redound at Dictionary.com
late 14c., "to overflow," from Old French redonder "overflow, abound, be in profusion" (12c.), from Latin redundare "to overflow" (see redundant). Meaning "to flow or go back" (to a place or person) is from late 14c.; hence "to rebound" (c.1500), and "to contribute to" (the credit, honor, etc.), early 15c. Related: Redounded; redounding.
redox (n.) Look up redox at Dictionary.com
1928, from red(uction) + ox(idation).
redress (v.) Look up redress at Dictionary.com
mid-14c., "to correct, reform;" late 14c., "restore, put right" (a wrong, error, offense); "repair; relieve; improve; amend," from Old French redrecier "reform, restore, rebuild" (Modern French redresser), from re- "again" (see re-) + drecier "to straighten, arrange" (see dress (v.)). Formerly used in many more senses than currently. Related: Redressed; redressing.
redressal (n.) Look up redressal at Dictionary.com
"a setting right again," 1800, from redress + -al (2). An earlier noun was simply redress "reparation, compensation, adjustment" (late 14c.), from Anglo-French redresce, Old French redrece, redresse
redshirt (v.) Look up redshirt at Dictionary.com
"to withdraw (a player) from the varsity team to add a year to his or her eligibility," 1955, in reference to the red shirts worn by athletes on the scrimmage squad; from red (adj.1) + shirt (n.).
redskin (n.) Look up redskin at Dictionary.com
"American Indian," 1690s, from red (adj.1) + skin (n.). Red as the skin color of Native Americans is from 1580s; red man is from 1580s. Also see red cent.
redstart (n.) Look up redstart at Dictionary.com
type of bird, 1560s, from red (adj.1) + start "tail," from Old English steort. Similar formation in German Rotsterz.
redtail (n.) Look up redtail at Dictionary.com
1812 in reference to a type of North American hawk; earlier used of various smaller European birds with red tail feathers (1550s); from red (adj.1) + tail (n.).
reduce (v.) Look up reduce at Dictionary.com
late 14c., "bring back," from Old French reducer (14c.), from Latin reducere "lead back, bring back," figuratively "restore, replace," from re- "back" (see re-) + ducere "bring, lead" (see duke (n.)). Meaning "bring to an inferior condition" is 1570s; that of "bring to a lower rank" is 1640s (military reduce to ranks is from 1802); that of "subdue by force of arms" is 1610s. Sense of "to lower, diminish, lessen" is from 1787. Related: Reduced; reducing.
reducible (adj.) Look up reducible at Dictionary.com
mid-15c.; see reduce + -ible. Compare Old French redusible.
reductio ad absurdum Look up reductio ad absurdum at Dictionary.com
Latin, literally "reduction to the absurd." Absurdum is neuter of absurdus. See reduction + absurd. The tactic is useful and unobjectionable in proofs in geometry.
reduction (n.) Look up reduction at Dictionary.com
early 15c., "a restoring to a former state; a subjugation" (of a people, etc.), from Middle French reducion (13c., Modern French réduction) and directly from Latin reductionem (nominative reductio) "a leading back, restoration," noun of action from past participle stem of reducere (see reduce). Meaning "diminution, a lessening" is from 1670s; chemical sense of "reversion to a simpler form" is from 1660s.
reductionism (n.) Look up reductionism at Dictionary.com
1948, in philosophy, from reduction in specialized sense in philosophy (1914) + -ism. Related: Reductionist.
reductionist (n.) Look up reductionist at Dictionary.com
1861 and after in various senses, from reduction + -ist. Philosophical sense, related to reductionism is from 1934.
reductive (adj.) Look up reductive at Dictionary.com
1630s, "that reduces;" 1650s, "that leads or brings back," from Medieval Latin reductivus, from reduct-, past participle stem of Latin reducere (see reduce). Related: Reductively.
redundance (n.) Look up redundance at Dictionary.com
1610s, from Latin redundantia "an overflowing, superfluity, excess," from redundare (see redundant).
redundancy (n.) Look up redundancy at Dictionary.com
c.1600; see redundant + -ancy. Sense in employment is from 1931, chiefly British.
redundant (adj.) Look up redundant at Dictionary.com
1590s, from Latin redundantem (nominative redundans), present participle of redundare, literally "overflow, pour over; be over-full;" figuratively "be in excess," from re- "again" (see re-) + undare "rise in waves," from unda "a wave" (see water (n.1)). Of persons, in employment situations, from 1928, chiefly British. Related: Redundantly.
reduplicate (v.) Look up reduplicate at Dictionary.com
1560s, from Medieval Latin reduplicatus, past participle of reduplicare "to redouble," from re- "back, again" (see re-) + Latin duplicare "to double" (see duplicate (adj.)). Related: Reduplicated; reduplicating; reduplicative.
reduplication (n.) Look up reduplication at Dictionary.com
1580s, from French réduplication (16c.), from Late Latin reduplicationem (nominative reduplicatio), noun of action from past participle stem of reduplicare (see reduplicate).
redux (adj.) Look up redux at Dictionary.com
"restored, brought back," Latin, from reducere (see reduce). In book titles at least since 1662 (Dryden, "Astraea Redux," written on the restoration of Charles II).
redware (n.) Look up redware at Dictionary.com
also red ware, type of pottery, 1690s, from red (adj.1) + ware (n.).
redwood (n.) Look up redwood at Dictionary.com
1610s, "wood that has a red hue," from red (adj.1) + wood (n.). Of various types of New World trees that yield such wood, from 1716; specifically of the California Sequoia sempervirens from 1819. In Scottish English 16c.-18c. the same word as an adjective meant "completely deranged, raving, stark mad," from wood (adj.).
reebok (n.) Look up reebok at Dictionary.com
South African antelope, 1775, from Dutch form of roebuck.
reed (n.) Look up reed at Dictionary.com
"tall, broad-leafed grass growing in wet places," Old English hreod "reed, rush," from Proto-Germanic *kreut- "reed" (cognates: Old Saxon hraid, Old Frisian hriad, Middle Dutch ried, Dutch riet, Old High German hriot, German Ried), with no known cognates beyond Germanic.

Meaning "musical pipe made from a reed stem" is from late 14c. (reed-pipe is from c.1300). As part of the mouthpiece of a musical instrument it is attested from 1520s. Meaning "a reed instrument" is from 1838.
reedy (adj.) Look up reedy at Dictionary.com
late 14c., "full of reeds," from reed + -y (2), or from Old English hreodig. Of tones, from 1811 in reference to musical reeds. Related: Reediness.
reef (n.1) Look up reef at Dictionary.com
"rock ridge underwater," 1580s, riffe, probably via Dutch riffe, from a Scandinavian source such as Old Norse rif "ridge in the sea; reef in a sail," literally "rib" (see rib (n.)).
reef (n.2) Look up reef at Dictionary.com
"horizontal section of sail," late 14c. (mid-14c. in rif-rope), from a Scandinavian source such as Old Norse rif "reef of a sail," probably a transferred use of rif "ridge under the sea; rib" (see rib (n.) and compare reef (n.1)). German reff, Swedish ref, Norwegian riv, Danish reb likely all are from the Old Norse word.
reef (v.) Look up reef at Dictionary.com
1660s, "take in, roll up" (as one would a section of a sail on a ship), from reef (n.2). Related: Reefed; reefing.
reefer (n.) Look up reefer at Dictionary.com
"marijuana cigarette," 1920s, perhaps an alteration of Mexican Spanish grifo "marijuana, drug addict" [OED]; or perhaps from reef (v.), on resemblance to a rolled sail. It also meant "pickpocket" in criminal slang (1935). Reefer also was a nickname for the sailing navy's equivalent to a midshipman (1818) "because they attend in the tops during the operation of reefing" [Century Dictionary], which is the source of the meaning "coat of a nautical cut" (1878) worn by sailors and fishermen "but copied for general use in the fashions of 1888-90" [CD].