Online Etymology Dictionary

braids (n.): 1520s; see braid (n.).
brail (n.): small rope used on ships, mid-15c., from Old French brail, earlier braiel "belt, leather thong," from Latin bracale "waistbelt," from bracæ "breeches" (plural, see breeches).
Braille: 1853, from Louis Braille (1809-1852), French musician and teacher, blind from age 3, who devised it c. 1830.
brain (n.): Old English brægen "brain," from Proto-Germanic *bragnam (source also of Middle Low German bregen, Old Frisian and Dutch brein), from PIE root *mregh-m(n)o- "skull, brain" (source also of Greek brekhmos "front part of the skull, top of the head"). But Liberman writes that brain "has no established cognates outside West Germanic ..." and is not connected to the Greek word. More probably, he writes, its etymon is PIE *bhragno "something broken."

The custom of using the plural to refer to the substance (literal or figurative), as opposed to the organ, dates from 16c. Figurative sense of "intellectual power" is from late 14c.; meaning "a clever person" is first recorded 1914. Brain teaser is from 1923. Brain stem first recorded 1879, from German. Brain drain is attested from 1963. An Old English word for "head" was brægnloca, which might be translated as "brain locker." In Middle English, brainsick (Old English brægenseoc) meant "mad, addled."
brain (v.): "to dash the brains out," late 14c., from brain (n.). Related: Brained; braining.
brain trust (n.): occasionally used since early 1900s, it became current in 1933, in reference to the intellectuals gathered by U.S. President Franklin D. Roosevelt as advisors; from brain (n.) + trust (n.).
brain-child (n.): "idea, creation of one's own," 1881, from brain (n.) + child. Earlier was the more alliterative brain-brat (1630).
brain-dead (adj.): 1976, popularized in U.S. by the Karen Anne Quinlan case (brain death is from 1968).
brainiac (n.): "very smart person," 1982, U.S. slang, from brain (n.) + ending from ENIAC, etc. Brainiac also was the name of a comic book villain in the Superman series and a do-it-yourself computer building kit, both from the late 1950s, and the word may bear traces of either or both of these.
brainstorm (n.): "brilliant idea, mental excitement, fit of mental application," 1849, from brain (n.) + figurative use of storm (n.). As a verb, recorded from 1920s. Related: Brainstormed; brainstorming.
brainwash (v.): 1955 (past participle adjective brainwashed attested from 1953); see brainwashing.
brainwashing (n.): 1950, a literal translation of Chinese xi nao. A term from the Korean War.
brainy (adj.): 1845, from brain (n.) + -y (2). Latin equivalent cerebrosus meant "passionate, hot-headed," leading Tucker to remark that " 'Brainy' is not a natural expression for 'frantic.' "
braise (v.): 1797, from French braiser "to stew" (17c.), from braise "live coals," from Old French brese "embers" (12c.), ultimately from West Germanic *brasa (as is Italian bragia, Spanish brasa), from PIE *bhre- "burn, heat" (see brawn). Related: Braised; braising.
brake (n.1): mid-15c., "instrument for crushing or pounding," from Middle Dutch braeke "flax brake," from breken "to break" (see break (v.)). The word was applied to many crushing implements and to the ring through the nose of a draught ox. It was influenced in sense by Old French brac, a form of bras "an arm," thus "a lever or handle," which was being used in English from late 14c., and applied to "a bridle or curb" from early 15c. One or the other or both took up the main modern meaning of "stopping device for a wheel," first attested 1772.
brake (n.2): kind of fern, early 14c.; see bracken.
brake (v.): "to apply a brake to a wheel," 1868, from brake (n.1). Earlier, "to beat flax" (late 14c.). Related: Braked; braking.
bramble (n.): Old English bræmbel "rough, prickly shrub" (especially the blackberry bush), with euphonic -b-, from earlier bræmel, from Proto-Germanic *bræmaz (see broom).
bran (n.): c. 1300, "the husk of wheat, barley, etc., separated from the flour after grinding," from Old French bren "bran, scurf, scales, feces" (12c., Modern French bran), perhaps connected with Gaulish *brenno- "manure," or with burn (v.). The word also was used 16c. in English for "dandruff flakes."
branch (n.): c. 1300, braunch, "limb of a tree" (also used of things analogous to it, especially geographic features), from Old French branche "branch, bough, twig; branch of a family" (12c.), from Late Latin branca "footprint," later "a claw, paw," which is of unknown origin, probably from Gaulish. The connecting notion would be the shape (compare pedigree). Replaced native bough. Meaning "local office of a business" is first recorded 1817, from earlier sense of "component part of a system" (1690s).
branch (v.): "send out shoots or new limbs," late 14c., also, of blood vessels, family trees, etc., "to be forked," from branch (n.). Meaning "to spread out from a center, radiate" is from c. 1400. Related: Branched; branching.
brand (n.): Old English brand, brond "fire, flame; firebrand, piece of burning wood, torch," and (poetic) "sword," from Proto-Germanic *brandaz (source also of Old Norse brandr, Old High German brant, Old Frisian brond "firebrand, blade of a sword," German brand "fire"), from root *bran-/*bren- (see burn (v.)). Meaning "identifying mark made by a hot iron" (1550s) broadened by 1827 to "a particular make of goods." Brand name is from 1922.
brand (v.): c. 1400, "to brand, cauterize; stigmatize," originally of criminal marks or cauterized wounds, from brand (n.). As a means of marking property, 1580s; figuratively from c. 1600, often in a bad sense, with the criminal marking in mind. Related: Branded; branding.
brand-new (adj.): 1570s, from brand (n.) + new. Originally it must have meant "fresh from the fire" (Shakespeare has fire-new).
Brandenburg: region in northeastern Germany, traditionally said to be ultimately from Slavic, but perhaps German and meaning literally "burned fortress," or else from a Celtic proper name.
brandish (v.): mid-14c., from Old French brandiss-, present participle stem of brandir "to flourish (a sword)" (12c.), from brant "blade of a sword, prow of a ship," of Frankish origin (see brand (n.)). Related: Brandished; brandishing.
brandy (n.): 1650s, abbreviation of brandywine (1620s) from Dutch brandewijn "burnt wine," so called because it is distilled (compare German cognate Branntwein and Czech palenka "brandy," from paliti "to burn"). The Brandywine Creek in Pennsylvania, site of a Revolutionary War battle, supposedly so named by the Dutch for the color of its waters.
branks (n.): 1590s, of unknown origin, perhaps from a North Sea Germanic language. An instrument of punishment for women, originally Scottish, it was a kind of iron cage for the head with a metal bit attached to still the tongue.
Paide for caring a woman throughe the towne for skoulding, with branks, 4d. ["Municipal Accounts of Newcastle," 1595]
"Ungallant, and unmercifully severe, as this species of torture seems to be, Dr. Plot, in his History of Staffordshire, much prefers it to the cucking stool, which, he says, 'not only endangers the health of the party, but also gives the tongue liberty 'twixt every dip.' " [Brockett, "A Glossary of North Country Words,"1829].
Branwen: fem. proper name, from Welsh bran "raven" + (g)wen "fair." Daughter of Llyr, she was one of the legendary heroines of Wales.
brash (adj.): 1824, of obscure origin, originally American English; perhaps akin to 16c. Scottish brash "attack, assault," or French breche "fragments," especially of ice, which is from a Germanic source (compare Old High German brehha "breach," from brehhan "to break"), or to German brechen "to vomit."
brass (n.): Old English bræs "brass, bronze," originally in reference to an alloy of copper and tin (now bronze), later and in modern use an alloy of two parts copper, one part zinc. A mystery word, with no known cognates beyond English. Perhaps akin to French brasser "to brew," because it is an alloy. It also has been compared to Old Swedish brasa "fire," but no sure connection can be made. Yet another theory connects it with Latin ferrum "iron," itself of obscure origin.

As brass was unknown in antiquity, use of the word in Bible translations, etc., likely means "bronze." The Romans were the first to deliberately make it. Words for "brass" in other languages (such as German Messing, Old English mæsling, French laiton, Italian ottone) also tend to be difficult to explain.

The meaning "effrontery, impudence" is from 1620s. Slang sense of "high officials" is first recorded 1899. The brass tacks that you get down to (1897) probably are the ones used to measure cloth on the counter of a dry goods store, suggesting precision. Slang brass balls "toughness, courage" (emphatically combining two metaphors for the same thing) attested by 1960s.
brasserie (n.): 1864, "brewery," from French brasserie, from Middle French brasser "to brew," from Latin brace "grain used to prepare malt," said by Pliny to be a Celtic word (compare Welsh brag "malt").
brassiere (n.): 18c., "woman's underbodice," from French brassière "child's chemise; shoulder strap" (17c.), from Old French braciere "arm guard" (14c.), from bras "an arm," from Latin bracchium (see brace (n.)). Modern use is a euphemistic borrowing employed in the garment trade by 1902.
brassy (adj.): "impudent," 1570s, from brass + -y (2). Compare brazen. Sense of "debased and pretentious" is from 1580s, from brass as contrasted with gold; sense of "strident and artificial" is from 1865. Related: Brassily; brassiness.
brat (n.): c. 1500, slang, "beggar's child," originally northern, Midlands and western England dialect word for "makeshift or ragged garment;" probably the same word as Old English bratt "cloak," which is from a Celtic source (compare Old Irish bratt "cloak, cloth"). The modern meaning is perhaps from notion of "child's apron." Hollywood Brat Pack (modeled on 1950s Rat Pack) is from 1985.
Bratislava: capital of Slovakia, a Slavic settlement named for its founder or chief; the name is the same element in the first half of the German name for the city, Pressburg (9c.).
bratty (adj.): "spoiled and juvenile," 1929, from brat + -y (2).
bratwurst (n.): 1911, from German Bratwurst, from wurst + Brät "lean meat, finely chipped calf or swine meat," from Old High German brato (12c.), from Proto-Germanic *bred-on- "roast flesh" (source also of Old English bræde "meat"), from PIE *bhreue- (see brawn). German folk etymology derives it from braten "to roast, bake, broil, grill;" more likely both are from the same ancient source.
Braun: German manufacturing company, named for founder Max Braun, mechanical engineer in Frankfurt am Main (1921).
bravado (n.): 1580s, from French bravade "bragging, boasting," from Italian bravata "bragging, boasting" (16c.), from bravare "brag, boast, be defiant," from bravo (see brave (adj.)). The English word was influenced in form by Spanish words ending in -ado.
brave (adj.): late 15c., from Middle French brave, "splendid, valiant," from Italian bravo "brave, bold," originally "wild, savage," possibly from Medieval Latin bravus "cutthroat, villain," from Latin pravus "crooked, depraved;" a less likely etymology being from Latin barbarus (see barbarous). A Celtic origin (Irish breagh, Cornish bray) also has been suggested.

Old English words for this, some with overtones of "rashness," included modig (now "moody"), beald ("bold"), cene ("keen"), dyrstig ("daring"). Brave new world is from the title of Aldous Huxley's 1932 satirical utopian novel; he lifted the phrase from Shakespeare ("Tempest" v.i.183).
brave (v.): "to face with bravery," 1776, from French braver, from brave (see brave (adj.)). Related: Braved; braving.
brave (n.): "North American Indian warrior," c. 1600, from brave (adj.), and compare bravo.
bravery (n.): 1540s, "daring, defiance, boasting," from French braverie, from braver "to brave" (see brave) or else from cognate Italian braveria, from bravare.
No Man is an Atheist, however he pretend it and serve the Company with his Braveries. [Donne, 1631]
As a good quality, attested from 1580s. Meaning "fine clothes" is from 1560s and holds the older sense.
bravo: as an exclamation, "well done!," 1761, from Italian bravo, literally "brave" (see brave (adj.)). Earlier it was used as a noun meaning "desperado, hired killer" (1590s). Superlative form is bravissimo.
It is held by some philologists that as "Bravo!" is an exclamation its form should not change, but remain bravo under all circumstances. Nevertheless "bravo" is usually applied to a male, "brava" to a female artist, and "bravi" to two or more. ["Elson's Music Dictionary," 1905]
bravura (n.): 1788, "piece of music requiring great skill," from Italian bravura "bravery, spirit" (see brave (adj.)). Sense of "display of brilliancy, dash" is from 1813.
braw: Scottish formation and pronunciation of brave.
brawl (v.): late 14c., braulen "to cry out, scold, quarrel," probably related to Dutch brallen "to boast," or from French brailler "to shout noisily," frequentative of braire "to bray" (see bray (v.)). Meaning "quarrel, wrangle, squabble" is from early 15c. Related: Brawled; brawling.
brawl (n.): mid-15c., from brawl (v.).
brawn (n.): late 13c., from Old French braon "fleshy or muscular part, buttock," from Frankish *brado "ham, roast" or some other Germanic source, from Proto-Germanic *bred-on- (source also of Old High German brato "tender meat," German Braten "roast," Old Norse brað "raw meat," Old English bræd "flesh"), from PIE *bhre- "burn, heat," from root *bhreuə- "to boil, bubble, effervesce, burn" (see brew (v.)). The original sense is "piece of meat suitable for roasting." "The specific sense 'boar's flesh' is exclusively of English development, and characteristic of English habits" [OED].