Online Etymology Dictionary

box (n.2.): "a blow," c. 1300, of uncertain origin, possibly related to Middle Dutch boke, Middle High German buc, and Danish bask, all meaning "a blow," perhaps imitative.
box (v.1): "to put into storage, put into a box," mid-15c., from box (n.1). Related: Boxed; boxing.
box (v.2): "to beat or whip," late 14c., from box (n.2). Meaning "to fight with the fists" is from 1560s. Related: Boxed; boxing.
box-top (n.): 1937, American English, from box (n.1) + top (n.1).
boxcar (n.): 1856, American English, from box (n.1) + car.
boxer (n.): "fighter," late 15c., agent noun from box (v.2). The name of the breed of dog (1934), is from German (the breed originated in Germany), itself taken from English boxer "fighter;" the dog so called for its pugnaciousness. Boxer shorts (1943) so called from their resemblance to the attire worn in the ring.
Boxer Rebellion: 1900, a name based on mistranslation of Chinese xenophobic society I-He-T'uan, "Righteous Harmony Band," rendered by British as I-He-Ch'uan "Righteous Uniting Fists," and so associated with the pugilistic boxer.
boxing (n.): "fighting with the fists as a sport," 1711, verbal noun from box (v.2).
Boxing Day (n.): 1809, "first weekday after Christmas," on which postmen and others expect to receive a Christmas present, originally in reference to the custom of distributing the contents of the Christmas box, which was placed in the church for charity collections. See box (n.1). The custom is older than the phrase.
boxy (adj.): 1858, from box (n.1) + -y (2). Related: Boxiness.
boy (n.): mid-13c., boie "servant, commoner, knave, boy," of unknown origin. Possibly from Old French embuie "one fettered," from Vulgar Latin *imboiare, from Latin boia "leg iron, yoke, leather collar," from Greek boeiai dorai "ox hides." (Words for "boy" double as "servant, attendant" across the Indo-European map -- compare Italian ragazzo, French garçon, Greek pais, Middle English knave, Old Church Slavonic otroku -- and often it is difficult to say which meaning came first.)

But it also appears to be identical with East Frisian boi "young gentleman," and perhaps with Dutch boef "knave," from Middle Dutch boeve, perhaps from Middle Low German buobe. This suggests a gradational relationship to babe. For a different conjecture:
In Old English, only the proper name Boia has been recorded. ME boi meant 'churl, servant' and (rarely) 'devil.' In texts, the meaning 'male child' does not antedate 1400. ModE boy looks like a semantic blend of an onomatopoeic word for an evil spirit (*boi) and a baby word for 'brother' (*bo). [Liberman]

A noticable number of the modern words for 'boy', 'girl', and 'child' were originally colloquial nicknames, derogatory or whimsical, in part endearing, and finally commonplace. These, as is natural, are of the most diverse, and in part obscure, origin. [Buck]
Used slightingly of young men in Middle English; meaning "male negro slave or Asian personal servant of any age" attested from c. 1600. Exclamation oh, boy attested from 1892.
boyar (n.): member of a Russian aristocratic class (abolished by Peter the Great), 1590s, from Russian boyarin, perhaps from boji "struggle," or from Slavic root *bol- "great."
boycott: 1880, noun and verb, from Irish Land League ostracism of Capt. Charles C. Boycott (1832-1897), land agent of Lough-Mask in County Mayo, who refused to lower rents for his tenant farmers. Quickly adopted by newspapers in languages as far afield as Japanese (boikotto). The family name is from a place in England.
Boyd: in many cases, the family name represents Gaelic or Irish buidhe "yellow," suggesting blond hair, compare Manx name Mac Giolla Buidhe (c. 1100).
boyfriend (n.): also boy-friend, "a woman's paramour," 1909, from boy + friend (n.).
boyish (adj.): 1540s, "pertaining to boys," from boy + -ish. Meaning "puerile" is from 1570s. Related: Boyishly; boyishness.
Boyle's law (n.): named for Irish-born chemist and physicist Robert Boyle (1627-1691), who published it in 1662.
boysenberry (n.): 1935, developed early 1900s by California botanist Rudolf Boysen (1895-1950) and named for him.
bozo (n.): "muscular low-I.Q. male," c. 1910, perhaps from Spanish bozal, used in the slave trade and also to mean "one who speaks Spanish poorly." Bozo the clown was created 1940 at Capitol Records as the voice in a series of story-telling records for children ["Wall Street Journal," Oct. 31, 1983].
bra (n.): by 1923, shortening of brassiere.
Brabant: region in eastern Belgium (in Middle Ages much more extensive), from Old High German brahha "newly broken land" (see break (v.)) + bant "region."
brace (n.): early 14c., "piece of armor for the arms," also "thong, strap for fastening," from Old French brace, braz "arms," also "length measured by two arms" (12c., Modern French bras "arm, power;" brasse "fathom, armful, breaststroke"), from Latin bracchia, plural of bracchium "an arm, a forearm," from Greek brakhion "an arm" (see brachio-). Applied to various devices for fastening and tightening on notion of clasping arms. Of dogs, "a couple, a pair" from c. 1400.
brace (v.): mid-14c., "to seize, grasp," also "wrap, enshroud; tie up, fetter," from Old French bracier "to embrace," from brace "arms" (see brace (n.)). Meaning "to render firm or steady by tensing" is mid-15c., earlier in figurative sense "strengthen or comfort" (someone), early 15c., with later extension to tonics, etc. that "brace" the nerves (compare bracer "stiff drink"). Related: Braced; bracing.
bracelet (n.): mid-15c., from Old French bracelet (14c.), diminutive of bracel, from Latin bracchiale "armlet," from bracchium "an arm, a forearm" (see brace (n.)).
bracer (n.): early 14c., "piece of armor protecting the arm;" 1580s, "a clamp, bind, brace," from brace (n.). Figurative sense of "that which braces the nerves" is 1740; especially of alcoholic drinks from c. 1850. Related: Bracers.
brach (n.): "bitch hound" (archaic), mid-14c., brache, originally "hound that hunts by scent," from Old French braches "hound, hunting dog," brachez, plural of brachet, of West Germanic origin (compare Middle Dutch brache, Old High German braccho "hound, setter"), from PIE *bhrag- "to smell" (source also of Middle High German bræhen "to smell," Latin fragrare "to smell sweetly"). Italian bracco is a Germanic loan word.
brachio-: before a vowel, brachi-, word-forming element meaning "arm," from Greek brakhion "arm," perhaps originally "upper arm," literally "shorter," and from brakhys "short" (see brief (adj.)), in contrast to the longer forearm.
brachiopod (n.): type of bivalve mollusk, 1836, Modern Latin, from Greek brakhion "arm" (see brachio-) + pous "foot," from PIE root *ped- (1) "a foot" (see foot (n.)). They have long spiral "arms" on either side of their mouths.
brachiosaurus (n.): 1903, Modern Latin, from Greek brakhion "arm" (see brachio-) + -saurus. The forelegs are notably longer than the hind legs.
brachy-: word-forming element meaning "short," from Latinized comb. form of Greek brakhys "short" (see brief (adj.)).
brack (adj.): "salty, briny," 1510s, from Dutch brak "brackish," probably from Middle Dutch brak "worthless," a word also used in commercial trade and which also made its way into early Modern English.
bracken (n.): "coarse fern," early 14c., a northern England word from a Scandinavian source (compare Danish bregne, Swedish bräken "fern").
bracket (n.): 1570s, bragget, "architectural support," probably from Middle French braguette "codpiece armor" (16c.), from a fancied resemblance of architectural supports to that article of attire (Spanish cognate bragueta meant both "codpiece" and "bracket"), diminutive of brague "knee pants," ultimately from Gaulish *braca "pants," itself perhaps from Germanic (compare Old English broc "garment for the legs and trunk;" see breeches). The architectural meaning also might reflect the "breeches" sense, on the notion of two limbs or of appliances used in pairs. The typographical bracket is first recorded 1750, so called for its resemblance to double supports in carpentry (a sense attested from 1610s). Senses affected by Latin brachium "arm."
bracket (v.): 1797, of printed matter, "to enclose in brackets," from bracket (n.). Also, "to couple or connect with a brace" (1827), also figurative, "to couple one thing with another" in writing (1807). Artillery rangefinding sense is from 1903, from the noun (1891) in the specialized sense "distance between the ranges of two shells, one under and one over the object." Related: Bracketed; bracketing. In home-building and joinery, bracketed is attested by 1801.
brackish (adj.): 1530s, from Scottish brack "salty" (see brack) + -ish. Related: Brackishness.
bract (n.): in botany, "small leaf at the base of a flower," Modern Latin, from Latin bractea, literally "thin metal plate," which is of unknown origin. Related: Bracteal; bracteate.
brad (n.): "small wire nail," late 13c., brod, from Old Norse broddr "spike, point, arrow," from Proto-Germanic *brozda- (source also of Old English brord "point, prick, blade of grass," Old High German brort "point, edge, crown"), from PIE *bhrs-dh-, from root *bhars- "projectile, point, bristle" (see bristle (n.)).
brady-: medical word-forming element meaning "slow, delayed, tardy," from Greek bradys "slow;" as in bradycardia (1890), with Latinized form of Greek kardia "heart;" bradykinesia, "slow movement," with Greek kinesis "movement, motion;" bradypnea, with Greek pneo/pnein "to breathe."
brae (n.): "steep slope," in northern England especially "the sides of a hill," early 14c., from Scottish, "slope, river bank," from Old Norse bra "eyelash," cognate with Old English bræw "eyelid," German Braue "eyebrow" (see brow). "The word must have passed through the sense of 'eye-brow' to 'brow of a hill', supercilium (cf. OE. eaghill 'eye-hill'=eyebrow)" [OED].
brag (v.): mid-14c., braggen "to make a loud sound," also "to talk boastfully," of obscure origin, perhaps related to bray of a trumpet, or related to the Middle English adjective brag "ostentatious, proud; spirited, brave" (early 14c.), which probably is from Celtic. Other sources suggest Old Norse bragr "the best, the toast (of anything)," also "poetry." Also see braggart for another possibility. Related: Bragged; bragging.
brag (n.): late 14c., "pomp; arrogance, pride;" see brag (v.); the exact relationship of the forms is uncertain. Meaning "that which is boasted" is from 1530s. As a once-popular poker-like card game, from 1734.
Braganza: city in Portugal (Portuguese Bragança), from Celtic briga "height"
braggadocio (n.): Spenser's coinage, 1590, as a name for his personification of vainglory, from brag, with augmentative ending by analogy to the Italian words then in vogue in England. In general use by 1594 for "an empty swaggerer;" of the talk of such persons, from 1734.
braggart (n.): 1570s, from French bragard (16c.), with pejorative ending (see -ard) + Middle French braguer "to flaunt, brag," perhaps originally "to show off clothes, especially breeches," from brague "breeches" (see bracket). There may be an element of codpiece-flaunting in all this.

The word in English has been at least influenced by brag (v.), even if, as some claim, it is unrelated to it. Bragger "arrogant or boastful person," agent noun from brag (v.), attested in English from late 14c.
Brahma: 1785, from Sanskrit Brahma, nominative of Brahman, chief god of the trinity Brahma-Vishnu-Siva in post-Vedic Hindu religion (see brahmin).
Brahman: see brahmin.
Brahmaputra: river in Asia, Hindi, literally "son of Brahma."
brahmin (n.): "member of Boston's upper class," 1823, figurative use of Brahman "member of the highest priestly Hindu caste," late 15c., from Sanskrit brahmana-s, from brahman- "prayer," also "the universal soul, the Absolute," which is of uncertain origin. Related to Brahma.
braid (v.): "to plait, knit, weave, twist together," c. 1200, breidan, from Old English bregdan "to move quickly, pull, shake, swing, throw (in wrestling), draw (a sword); bend, weave, knit, join together; change color, vary; scheme, feign, pretend" (class III strong verb, past tense brægd, past participle brogden), from Proto-Germanic *bregthan "make sudden jerky movements from side to side" (compare Old Norse bregða "to brandish, turn about, braid;" Old Saxon bregdan "to weave;" Dutch breien "to knit;" Old High German brettan "to draw, weave, braid"), from PIE root *bherek- "to gleam, flash" (compare Sanskrit bhrasate "flames, blazes, shines"). In English the verb survives only in the narrow definition of "plait hair." Related: Braided; braiding.
braid (n.): in part from stem found in Old English gebrægd "craft, fraud," gebregd "commotion," Old Norse bragð "deed, trick," and in part from or influenced by related braid (v.). Earliest senses are "a deceit, stratagem, trick" (c. 1200), "sudden or quick movement" (c. 1300); meaning "anything plaited or entwined" (especially hair) is from 1520s.