redhead (n.)
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.)
also re-dial, 1961, from re- + dial (v.). Related: Redialed; redialing.
redingote (n.)
"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.)
1805 (implied in redirected), from re- "back, again" + direct (v.). Related: Redirecting.
rediscover (v.)
1752, from re- + discover (v.). Related: Rediscovered; rediscovering.
rediscovery (n.)
1747, from re- + discovery.
redistribute (v.)
1610s, from re- "back, again" + distribute. Related: Redistributed; redistributing.
redistribution (n.)
1831, from French redistribution; see re- + distribution.
redistributive (adj.)
1860, from redistribute + -ive. Related: Redistributively.
redistrict (v.)
"redraw the boundaries of districts," 1838, in U.S. political sense, from re- "again" + district. Related: Redistricted; redistricting.
redivide (v.)
c.1600, from re- + divide (v.). Related: Redivided; redividing.
redline (v.)
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.)
"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.)
Old English readnes; see from red (adj.1) + -ness.
redo (v.)
also re-do, 1590s, from re- "back, again" + do (v.). Related: Redone; redoing.
redolence (n.)
early 15c., from Old French redolence, related to redolent (see redolent).
redolent (adj.)
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.)
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.)
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.)
late 14c., from Old French redoutable (12c.), from redouter "to dread," from re-, intensive prefix, + douter "be afraid of" (see doubt (v.)).
redound (v.)
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.)
1928, from red(uction) + ox(idation).
redress (v.)
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.)
"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.)
"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.)
"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.)
type of bird, 1560s, from red (adj.1) + start "tail," from Old English steort. Similar formation in German Rotsterz.
redtail (n.)
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.)
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.)
mid-15c.; see reduce + -ible. Compare Old French redusible.
reductio ad absurdum
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.)
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.)
1948, in philosophy, from reduction in specialized sense in philosophy (1914) + -ism. Related: Reductionist.
reductionist (n.)
1861 and after in various senses, from reduction + -ist. Philosophical sense, related to reductionism is from 1934.
reductive (adj.)
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.)
1610s, from Latin redundantia "an overflowing, superfluity, excess," from redundare (see redundant).
redundancy (n.)
c.1600; see redundant + -ancy. Sense in employment is from 1931, chiefly British.
redundant (adj.)
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.)
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.)
1580s, from French réduplication (16c.), from Late Latin reduplicationem (nominative reduplicatio), noun of action from past participle stem of reduplicare (see reduplicate).
redux (adj.)
"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.)
also red ware, type of pottery, 1690s, from red (adj.1) + ware (n.).
redwood (n.)
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.)
South African antelope, 1775, from Dutch form of roebuck.
reed (n.)
"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.)
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)
"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)
"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.)
1660s, "take in, roll up" (as a sail on a ship), from reef (n.2). Related: Reefed; reefing.
reefer (n.)
"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 "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].