box-kite (n.) Look up box-kite at Dictionary.com
1898, from box (n.1) + kite (n.), so called for its shape.
box-office (n.) Look up box-office at Dictionary.com
"office in a theater in which tickets are sold," 1786, from box (n.1) + office (n.). Box is from late 14c. in the specialized sense "money box," especially one in which money is kept for some particular purpose; extended to "funds, money" before c. 1400. Box office in the figurative sense of "financial element of a performance" is recorded by 1904.
box-top (n.) Look up box-top at Dictionary.com
1937, American English, from box (n.1) + top (n.1).
box-turtle (n.) Look up box-turtle at Dictionary.com
1825, American English for what is called by English writers a box-tortoise (1834), from box (n.1), so called for its resemblance to a tight, closed box when the head, tail, and legs are drawn in.
boxcar (n.) Look up boxcar at Dictionary.com
also box-car, "large enclosed railroad car for goods," 1856, American English, from box (n.1) + car.
boxer (n.) Look up boxer at Dictionary.com
"fist-fighter, pugilist," late 15c., agent noun from box (v.2). The breed of dog (1934), is from German Boxer (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 (n.) Look up Boxer Rebellion at Dictionary.com
1900, a name based on a mistranslation of the name of a 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.
boxiana (n.) Look up boxiana at Dictionary.com
"the lore and annals of prize-fighting," by 1819, mock-Latin, from box (v.2).
boxing (n.) Look up boxing at Dictionary.com
"fighting with the fists as a sport," 1711, verbal noun from box (v.2). Boxing glove "padded glove used in sparring" is from 1805.
Boxing Day (n.) Look up Boxing Day at Dictionary.com
1809, "first weekday after Christmas," on which by an English custom postmen, employees, and others can 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.
boxwood (n.) Look up boxwood at Dictionary.com
also box-wood, "wood of the box-tree," fine and hard-grained, used for handles, etc., 1650s, from box (n.3) + wood (n.).
boxy (adj.) Look up boxy at Dictionary.com
"like a box in shape," 1858, from box (n.1) + -y (2). Related: Boxiness.
boy (n.) Look up boy at Dictionary.com
mid-13c., boie "servant, commoner, knave" (generally young and male); c. 1300, "rascal, ruffian, knave; urchin," mid-14c. as "male child before puberty" (possibly an extended sense from the "urchin" one. A word 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, also in familiar or contemptuous use of criminal toughs or men in the armed services. In some local uses "a man," without reference to age (OED lists "in Cornwall, in Ireland, in the far West of the U.S."). Meaning "male negro slave or Asian personal servant of any age" attested from c. 1600. Extended form boyo is attested from 1870. Emphatic exclamation oh, boy attested from 1892. Boy-meets-girl "typical of a conventional romance" is from 1945; the phrase itself is from 1934 as a dramatic formula. Boy-crazy "eager to associate with males" is from 1923.
boyar (n.) Look up boyar at Dictionary.com
member of a Russian aristocratic class, 1590s, from Russian boyarin (plural boyare), perhaps from boji "struggle," or from Slavic root *bol- "great." Originally a title (abolished by Peter the Great) of officials, it came to signify the Russian aristocracy generally.
boycott Look up boycott at Dictionary.com
1880, noun and verb, "to combine in refusing to have dealings with, and preventing or discouraging others from doing so, as punishment for political or other differences." 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. Related: Boycotted; boycotter; boycotting.
Boyd Look up Boyd at Dictionary.com
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.) Look up boyfriend at Dictionary.com
also boy-friend, "favorite male companion" (with implication of romantic connection), "a woman's paramour," 1909, from boy + friend (n.). Earlier in a non-romantic sense "juvenile male companion" (1850).
boyhood (n.) Look up boyhood at Dictionary.com
"state of being a boy; the earely period of a male's life," 1745, from boy + -hood.
boyish (adj.) Look up boyish at Dictionary.com
1540s, "pertaining to boys," from boy + -ish. Meaning "puerile" is from 1570s. Related: Boyishly; boyishness.
Boyle's law (n.) Look up Boyle's law at Dictionary.com
named for Irish-born chemist and physicist Robert Boyle (1627-1691), who published it in 1662.
boysenberry (n.) Look up boysenberry at Dictionary.com
1935, developed early 1900s by California botanist Rudolf Boysen (1895-1950) and named for him.
bozo (n.) Look up bozo at Dictionary.com
c. 1924, "muscular low-I.Q. male," 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].
br'er Look up br'er at Dictionary.com
also brer, in Br'er Rabbit, etc., 1881, Joel Chandler Harris' representation of U.S. Southern black pronunciation of brother.
bra (n.) Look up bra at Dictionary.com
by 1923, shortening of brassiere.
Brabant Look up Brabant at Dictionary.com
region in eastern Belgium (in the Middle Ages a duchy and much more extensive), from Old High German brahha "newly broken land" (see break (v.)) + bant "region." Related: Brabançon; Brabanter; Brabantine.
brace (v.) Look up brace at Dictionary.com
mid-14c., "to seize, grasp, hold firmly," also "wrap, enshroud; tie up, fetter," from Old French bracier "to embrace," from brace "arms" (see brace (n.)). Meaning "make tense, 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"). To brace oneself "place oneself in the position of a brace" (in anticipation of some shock or impact) is by 1805, perhaps c. 1500. To brace up "increase the tension or vigor of" is from 1809. Related: Braced; bracing.
brace (n.) Look up brace at Dictionary.com
early 14c., "piece of armor for the arms," also "thong, strap for fastening," from Old French brace "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-).

Meaning "that which holds two or more things firmly together" (on notion of clasping arms) is from mid-15c. Hence applied to various devices for fastening and tightening. Meaning "a prop, support," especially in architecture, is from 1520s. Of dogs, ducks, pistols, etc., "a couple, a pair" from c. 1400. Braces is from 1798 as "straps passing over the shoulders to hold up the trousers;" from 1945 as "wires for straightening the teeth."
bracelet (n.) Look up bracelet at Dictionary.com
"ornamental ring or clasped chain for the wrist," mid-15c., from Old French bracelet (14c.), diminutive of bracel, from Latin bracchiale "armlet," from bracchium "an arm, a forearm," from Greek brakhion "an arm" (see brachio-).
bracer (n.) Look up bracer at Dictionary.com
early 14c., "piece of armor protecting the arm;" 1580s, "a clamp, bind, that which braces or makes firm," agent noun from brace (v.). Figurative sense of "that which braces the nerves" is 1740; especially an alcoholic drink taken early in the morning (by 1826). Related: Bracers.
brach (n.) Look up brach at Dictionary.com
"bitch hound" (archaic), mid-14c., brache, originally "hound that hunts by scent," from Old French braches "hound, hunting dog," brachez, plural of brachet, a word of West Germanic origin (compare Middle Dutch brache, Old High German braccho "hound, setter"), from PIE root *bhrag- "to smell" (source also of Middle High German bræhen "to smell," Middle Irish bren "putrid, foul," perhaps also Latin fragrare "to smell sweetly"). Italian bracco is a Germanic loan word.
brachial (adj.) Look up brachial at Dictionary.com
"belonging to the arm, fore-leg, wing," etc., 1570s, from Latin brachialis, from brachium (see brachio-).
brachio- Look up brachio- at Dictionary.com
before a vowel, brachi-, word-forming element meaning "arm, of the upper arm, pertaining to the upper arm and," from Greek brakhion "arm," perhaps originally "upper arm," literally "shorter," from brakhys "short" (from PIE root *mregh-u- "short"), in contrast to the longer forearm.
brachiopod (n.) Look up brachiopod at Dictionary.com
type of bivalve mollusk of the class Brachiopoda, 1836, Modern Latin, from Greek brakhion "an arm" (see brachio-) + pous "foot" (from PIE root *ped- "foot"). They develop long spiral "arms" from either side of their mouths.
brachiosaurus (n.) Look up brachiosaurus at Dictionary.com
1903, Modern Latin, from Greek brakhion "an arm" (see brachio-) + -saurus. The forelegs are notably longer than the hind legs.
brachy- Look up brachy- at Dictionary.com
word-forming element meaning "short," from Latinized combining form of Greek brakhys "short," from PIE root *mregh-u- "short."
brachycephalic (adj.) Look up brachycephalic at Dictionary.com
in ethnology, "short-headed," 1847; see brachy- + cephalic. Denoting skulls at least 80 percent as wide as they are long (considered typical of Mongoloid peoples). Related: Brachycephalous; brachycephalism.
brack (adj.) Look up brack at Dictionary.com
"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.) Look up bracken at Dictionary.com
"coarse fern," c. 1300, a northern England word, probably from a Scandinavian source (compare Danish bregne, Swedish bräken "fern"), from Proto-Germanic *brak- "undergrowth, bushes," from PIE root *bhreg- "to break" on the notion of "that which impedes motion" [Watkins].
bracket (v.) Look up bracket at Dictionary.com
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.
bracket (n.) Look up bracket at Dictionary.com
1570s, bragget, "architectural support, supporting piece projecting from a vertical surface," probably from Middle French braguette, originally "codpiece armor" (16c.), from a fancied resemblance of architectural supports to that article of attire (Spanish cognate bragueta meant both "codpiece" and "projecting moulding in architecture"), 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 be directly from the "breeches" sense, on the notion of two limbs or of appliances used in pairs. The senses have been affected by Latin brachium "arm." The typographical bracket ("marks used to enclose a note, reference, explanation, etc.," formerly called crotchets) is first recorded 1750, so called for its resemblance to double supports in carpentry (a sense attested from 1610s). Meaning "position of being enclosed or bracketed with others" as of equal standing is from 1880.
brackish (adj.) Look up brackish at Dictionary.com
of water, "somewhat salty," 1530s, from Scottish brack "salty" (see brack) + -ish. Related: Brackishness.
bract (n.) Look up bract at Dictionary.com
in botany, "small leaf beneath a flower," Modern Latin, from Latin bractea, literally "thin metal plate," a word of unknown origin. Related: Bracteal; bracteate.
brad (n.) Look up brad at Dictionary.com
"small flat nail having instead of a head a slight projection on one side," 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.)).
Bradley Look up Bradley at Dictionary.com
masc. proper name, originally a surname, from various places in England, literally "the broad clearing," from Old English elements brad (see broad (adj.)) + leah (see lea). Most popular in U.S. c. 1965-1995.
brady- Look up brady- at Dictionary.com
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.) Look up brae at Dictionary.com
"steep slope," in northern England especially "the side of a hill," early 14c., from Scottish, "slope, river bank," perhaps 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 (n.) Look up brag at Dictionary.com
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.
brag (v.) Look up brag at Dictionary.com
late 14c., braggen "to make a loud sound," also "to talk boastfully," of obscure origin, perhaps related to bray of a trumpet and imitative, or related to the Middle English adjective brag "ostentatious, proud; spirited, brave" (early 14c.), which probably is from Celtic, and is the source of the surname Bragg (attested from mid-13c.). Perhaps a merger of the two. Other sources suggest Old Norse bragr "the best, the toast (of anything)," also "poetry." Also see braggart for another possibility, but French brague seems too late to be the source. Related: Bragged; bragging.
Braganza Look up Braganza at Dictionary.com
city in Portugal (Portuguese Bragança), from Celtic briga "height"
braggadocio (n.) Look up braggadocio at Dictionary.com
1590, coined by Spenser as the name of his personification of vainglory ("Faerie Queene," ii.3), from brag, with augmentative ending from Italian words then in vogue in English. In general use by 1594 for "an empty swaggerer;" of the talk of such persons, from 1734.