refraction (n.)
1570s, from Late Latin refractionem (nominative refractio) "a breaking up," noun of action from past participle stem of Latin refringere "to break up," from re- "back" (see re-) + comb. form of frangere "to break" (see fraction).
refractive (adj.)
1670s, from Late Latin refractivus, or from refract + -ive.
refractor (n.)
1769, as a type of telescope, agent noun from refract.
refractory (adj.)
"stubborn, obstinate, perverse," 1610s (earlier refractorious, 1550s, refractary, c.1600), from Latin refractarius "obstinate, stubborn," from past participle stem of refringere (see refraction). Related: Refractorily; refractoriness.
refrain (v.)
mid-14c., from Old French refraigner "restrain, repress, keep in check" (12c., Modern French Réfréner), from Latin refrenare "to bridle, hold in with a bit, check, curb, keep down, control," from re- "back" (see re-) + frenare "restrain, furnish with a bridle," from frenum "a bridle." Related: Refrained; refraining.
refrain (n.)
late 14c., from Old French refrain "chorus" (13c.), alteration of refrait, noun use of past participle of refraindre "repeat," also "break off," from Vulgar Latin *refrangere "break off," alteration of Latin refringere "break up, break open" (see refraction) by influence of frangere "to break." Influenced in French by cognate Provençal refranhar "singing of birds, refrain." The notion is of something that causes a song to "break off" then resume. OED says not common before 19c.
reframe (v.)
1580s, from re- + frame (v.). Related: Reframed; reframing.
refrangible (adj.)
1670s, from stem of Vulgar Latin *refrangere, from re- "back" (see re-) + Latin frangere "to break" (see fraction).
refresh (v.)
late 14c., from Old French refreschier "refresh, renew" (12c.; Modern French rafraîchir), from re- "again" (see re-) + fresche "fresh" (Modern French frais), from a Germanic source (such as Old High German frisc "fresh," see fresh (adj.)). Related: Refreshed; refreshing.
refreshing (adj.)
1570s, present participle adjective from refresh (v.). Mental or spiritual sense is attested from 1690s. Related: Refreshingly.
refreshment (n.)
late 14c., "act or fact of refreshing," originally mental and spiritual, from Old French refreschement (Modern French rafraîchissement, from refreschier (see refresh). Refreshments, of food and drink only, from 1660s.
refrigerant (adj.)
1590s, originally in medicine; from Latin refrigerans, present participle of refrigerare "make cool or cold" (see refrigeration). As a noun from 1670s.
refrigerate (v.)
1530s, back-formation from refrigeration, or else from Latin refrigeratus, past participle of refrigerare "make cool or cold." Related: Refrigerated; refrigerating. Earlier words in the same sense of "to make cold, to cool" were infrigiden, infrigidate (both early 15c.).
refrigeration (n.)
late 15c., "act of cooling or freezing," from Latin refrigerationem (nominative refrigeratio) "a cooling, mitigation of heat," especially in sickness, noun of action from past participle stem of refrigerare, from re- "again" (see re-) + frigerare "make cool," from frigus (genitive frigoris) "cold" (see frigid). Specifically "freezing provisions as a means of preserving them" from 1881.
refrigerator (n.)
1610s, "something that cools," agent noun from refrigerate. As "cabinet for keeping food cool," 1824, originally in the brewery trade, in place of earlier refrigeratory (c.1600). The electric-powered household device was available from c.1918.
refry (v.)
1957, in refried beans, which translates Spanish frijoles refritos. From re- + fry (v.).
reft
past participle of reave.
refuel (v.)
also re-fuel, 1811, from re- "again" + fuel (v.). Originally in a spiritual sense. Related: Refueled; refuelling.
refuge (n.)
"shelter or protection from danger or distress," late 14c., from Old French refuge "hiding place" (12c.), from Latin refugium "a taking refuge; place to flee back to," from re- "back" (see re-) + fugere "to flee" (see fugitive) + -ium "place for."
refugee (n.)
1680s, from French refugié, noun use of past participle of refugier "to take shelter, protect," from Old French refuge (see refuge). First applied to French Huguenots who migrated after the revocation (1685) of the Edict of Nantes. The word meant "one seeking asylum," till 1914, when it evolved to mean "one fleeing home" (first applied in this sense to civilians in Flanders heading west to escape fighting in World War I). In Australian slang from World War II, reffo.
refulgence (n.)
1630s, from Latin refulgentia "reflected luster, splendor," from refulgens (see refulgent). Related: Refulgency (1610s).
refulgent (adj.)
c.1500, from Middle French refulgent or directly from Latin refulgentem (nominative refulgens), present participle of refulgere "flash back, shine brilliantly," from re- "back" (see re-) + fulgere "to shine" (see bleach (v.)).
refund (v.)
"to give back, restore," early 15c. (earlier "to pour back," late 14c.), from Old French refunder "restore" and directly from Latin refundere "give back, restore, return," literally "pour back, flow back," from re- "back" (see re-) + fundere "to pour" (see found (v.2)). Specifically of money from 1550s. Related: Refunded; refunding.
refund (n.)
"a return of money paid," 1782, from refund (v.).
refurbish (v.)
1610s, from re- "again" + furbish, on model of French refourbir. Related: Refurbished; refurbishing.
refusal (n.)
late 15c., from refuse + -al (2).
refuse (v.)
c.1300, from Old French refuser "reject, disregard, avoid" (12c.), from Vulgar Latin *refusare, frequentative form from past participle stem of Latin refundere "pour back, give back" (see refund (v.)). Related: Refused; refusing.
refuse (n.)
mid-14c., "an outcast;" mid-14c., "a rejected thing, waste material, trash," from Old French refus "waste product, rubbish; refusal, denial, rejection," a back-formation from the past participle of refuser (see refuse (v.)). As an adjective from late 14c., "despised, rejected;" early 15c., "of low quality."
Refusenik (n.)
"Soviet Jew who has been refused permission to emigrate to Israel," 1975, a partial translation of Russian otkaznik, from otkazat "to refuse;" with English refuse (v.). Also see -nik.
refutation (n.)
1540s, from Middle French réfutation (16c.) and directly from Latin refutationem (nominative refutatio) "disproof of a claim or argument," noun of action from past participle stem of refutare (see refute).
refute (v.)
1510s, "refuse, reject," from Middle French réfuter (16c.) and directly from Latin refutare "drive back; rebut, disprove; repress, repel, resist, oppose," from re- "back" (see re-) + -futare "to beat," probably from PIE root *bhau- "to strike down" (see bat (n.1)).

Meaning "prove wrong" dates from 1540s. Since c.1964 linguists have frowned on the subtle shift in meaning towards "to deny," as it is used in connection with allegation. Related: Refuted; refuting.
reg (n.)
1952 as a shortening of regulation.
regain (v.)
1540s, from Middle French regaigner (Modern French regagner), from re- "again" (see re-) + gaginer, from Old French gaaignier (see gain (v.)). Related: Regained; regaining.
regal (adj.)
late 14c., from Old French regal "royal" (12c.) or directly from Latin regalis "royal, kingly; of or belonging to a king, worthy of a king," from rex (genitive regis) "king," from PIE root *reg- "move in a straight line," hence, "direct in a straight line, rule, guide" (cognates: Sanskrit raj- "a king, a leader;" Avestan razeyeiti "directs;" Persian rahst "right, correct;" Latin regere "to rule," rex "a king, a leader," rectus "right, correct;" Old Irish ri, Gaelic righ "a king;" Gaulish -rix "a king," in personal names, such as Vircingetorix; Gothic reiks "a leader;" Old English rice "kingdom," -ric "king," rice "rich, powerful," riht "correct;" Gothic raihts, Old High German recht, Old Swedish reht, Old Norse rettr "correct"). Related: Regally.
regale (v.)
"entertain splendidly," 1650s, from French régaler "to entertain or feast," from Old French regale, rigale, from gale "merriment," from galer "make merry" (see gallant (adj.)). Influenced in Old French by se rigoler "amuse oneself, rejoice," of unknown origin. Italian regalo is from French. Related: Regaled; regaling.
regalia (n.)
1530s, "rights and powers of a king, royal privilege," from Latin regalia "royal things," noun use of neuter plural of regalis (see regal). Meaning "decorations or insignia of an order" first recorded 1670s.
regard (n.)
mid-14c., "a consideration; a judgment," from Old French regard, from regarder "take notice of," from re-, intensive prefix + garder "look, heed," from Germanic (see guard (n.)). Meanings "a look, appearance; respect, esteem, favor, kindly feeling which springs from a consideration of estimable qualities" all recorded late 14c. Phrase in regard to is from mid-15c. (Chaucer uses at regard of).
regard (v.)
mid-14c., "consider" (that something is so), from Middle French regarder "to look at," from regard (see regard (n.)). Meaning "look upon, observe" is from 1520s, as is that of "observe a certain respect toward." Related: Regarded; regarding.
regardless (adj.)
"indifferent," 1590s, from regard (n.) + -less. Elliptical for "regardless of consequences, expenses, etc.," from 1872.
regards (n.)
plural of regard (n.). In letters, from 1775, from regard in the sense of "esteem, affection" (late 14c.).
regatta (n.)
1650s, name of a boat race among gondoliers held on the Grand Canal in Venice, from Italian (Venetian dialect) regatta, literally "contention for mastery," from rigattare "to compete, haggle, sell at retail." [Klein's sources, however, suggest a source in Italian riga "row, rank," from a Germanic source and related to English row (v.).] The general meaning of "boat race, yacht race" is usually considered to have begun with a race on the Thames by that name June 23, 1775 (see OED), but there is evidence that it was used as early as 1768.
regency (n.)
early 15c., "government by regents," from Medieval Latin regentia, from Latin regens (see regent). Notable instances were: France 1715-1723 (under Philip, Duke of Orleans), Britain 1811-1820 (under George, Prince of Wales, Prince Regent), "in each case with suggestion of debauchery" [Weekley]. In reference to the style of that time, attested from 1880 (there is an unexplained use in Jane Austen from 1793). Compare French equivalent Régence, attested in English from 1919. U.S. Albany Regency refers to dominant political faction in New York state c.1820-1850.
regeneracy (n.)
1620s; see regenerate + -cy.
regenerate (adj.)
mid-15c., from Latin regeneratus, past participle of regenerare "bring forth again" (see regeneration).
regenerate (v.)
1550s, back-formation from regeneration or else from Latin regeneratus, past participle of regenerare "bring forth again" (see regeneration). Originally religious; of body parts from 1590s. Related: Regenerated; regenerating. Replaced earlier regeneren (c.1400), from Old French regenerer.
regeneration (n.)
mid-14c., from Late Latin regenerationem (nominative regeneratio) "a being born again," noun of action from past participle stem of Latin regenerare "make over, generate again," from re- "again" (see re-) + generare "to produce" (see generation). Originally spiritual; of animal tissue, early 15c.; of forests, 1888.
regenerative (adj.)
late 14c., from Old French regeneratif or directly from Medieval Latin regenerativus, from regeneratus, past participle of regenerare "bring forth again" (see regeneration).
regent (n.)
"one who rules during the minority or absence of a sovereign," c.1400, from the adjective (now archaic, attested in English late 14c.), from Old French regent and directly from Medieval Latin regentem (nominative regens), from Latin regens "ruler, governor," noun use of present participle of regere "to rule, direct" (see regal). Senses of "university faculty member" is attested from mid-15c., originally Scottish.
reggae (n.)
1968, Jamaican English (first in song title "Do the Reggay" by Toots & the Maytals), perhaps [OED, Barnhart] related to rege-rege "a quarrel, protest," literally "ragged clothes," variant of raga-raga, alteration and reduplication of English rag (n.).
regicide (n.)
1540s, "man who kills a king," formed from Latin rex (genitive regis) "king" (see regal) on model of suicide. Meaning "crime of killing a king" is from c.1600.