butternut (n.) Look up butternut at Dictionary.com
also butter-nut, 1753, nut of the white walnut, a North American tree; transferred to the tree itself from 1783. The nut's color was a brownish-gray, hence the word was used (1861) to describe the warm gray color of the Southern army uniforms in the American Civil War.
buttery (adj.) Look up buttery at Dictionary.com
"resembling butter," late 14c., from butter (n.) + -y (2). Related: Butteriness.
buttery (n.) Look up buttery at Dictionary.com
"place for storing liquor," originally "room where provisions are laid up" (late 14c.), from Old French boterie, from Late Latin botaria, from bota, variant of butta "cask, bottle;" see butt (n.2) + -ery.
butthead (n.) Look up butthead at Dictionary.com
also butt-head, late 1980s, student slang, "objectionable person," from butt (n.1) + head (n.); perhaps influenced by butterhead, 1960s African-American vernacular for one who is a disgrace to the community. Earlier, butthead meant simply "the butt end, bottom" of anything (1630s).
butthole (n.) Look up butthole at Dictionary.com
also butt-hole, "anus," 1950s slang, from butt (n.1) + hole (n.). Earlier it meant "blind hole; cul-de-sac" (early 20c.).
buttinski (n.) Look up buttinski at Dictionary.com
a jocular name for one who cuts into a line, etc., 1902, American English, from verbal phrase butt in (see butt (v.)) + surname ending based on Eastern European names.
buttock (n.) Look up buttock at Dictionary.com
late 13c., singular of buttocks (q.v.).
buttocks (n.) Look up buttocks at Dictionary.com
late 13c., probably related to Old English buttuc "end, short piece of land," from Proto-Germanic *butaz, from PIE root *bhau- "to strike."
button (v.) Look up button at Dictionary.com
late 14c., "to furnish with buttons;" early 15c., "to fasten with buttons" (of a garment,) from button (n.) or from Old French botoner (Modern French boutonner), from boton (n.) "button," which is from the same Germanic source as the English word. Related: Buttoned; buttoning. Button-down (adj.) in reference to shirt collars is from 1916.
button (n.) Look up button at Dictionary.com
c. 1300 (surname Botouner "button-maker" attested from mid-13c.), from Old French boton "a button," originally "a bud" (12c., Modern French bouton), from bouter, boter "to thrust, strike, push," common Romanic (cognate with Spanish boton, Italian bottone), ultimately from Germanic, from Proto-Germanic *buttan, from PIE root *bhau- "to strike." Thus a button is, etymologically, something that pushes up, or thrusts out.

Meaning "point of the chin" is pugilistic slang, by 1921. A button as something you push to create an effect by closing an (electrical) circuit is attested from 1840s. Button-pusher as "deliberately annoying or provocative person" is attested by 1990 (in reference to Bill Gates, in "InfoWorld" magazine, Nov. 19). In the 1980s it meant "photographer."
button-hole (n.) Look up button-hole at Dictionary.com
1560s, from button (n.) + hole (n.). The verb, also buttonhole, meaning "to detain (someone) in conversation against his will" (1862) was earlier button-hold (1834), from button-holder (1806, in this sense). The image is of holding someone by the coat-button so as to detain him.
buttonwood (n.) Look up buttonwood at Dictionary.com
also button-wood, "North American plane tree," 1690s, from button (n.) + wood (n.). So called for their characteristic round fruit.
buttress (v.) Look up buttress at Dictionary.com
late 14c., literal and figurative, from buttress (n.). Related: Buttressed; buttressing.
buttress (n.) Look up buttress at Dictionary.com
early 14c., from Old French (arc) botrez "flying buttress," apparently from bouter "to thrust against," of Frankish origin (compare Old Norse bauta "to strike, beat"), from Proto-Germanic *butan, from PIE root *bhau- "to strike."
butty (n.) Look up butty at Dictionary.com
"slice of bread and butter," 1855, northern English, from butter (n.) + -y (2).
butyl (n.) Look up butyl at Dictionary.com
hydrocarbon radical, 1868, from butyric acid, a product of fermentation found in rancid butter, from Latin butyrum "butter" (see butter (n.)).
butyric (adj.) Look up butyric at Dictionary.com
1826, from stem of Latin butyrum "butter" (see butter (n.)) + -ic.
buxom (adj.) Look up buxom at Dictionary.com
late 12c., buhsum "humble, obedient," from Old English bugen "to bow" (from Proto-Germanic *bugan-, from PIE root *bheug- "to bend") + -som (see -some (1)), for a total meaning "capable of being bent." Meaning progressed from "compliant, obliging," through "lively, jolly," "healthily plump, vigorous," to (in women, and perhaps influenced by lusty) "plump, comely" (1580s). In Johnson [1755] the primary meaning still is "obedient, obsequious."

Used often of breasts, and by 1950s it had begun to be used more narrowly for "bosomy" and could be paired with slim (adj.). Dutch buigzaam, German biegsam "flexible, pliable" hew closer to the original sense of the English cognate.
buy (v.) Look up buy at Dictionary.com
Old English bycgan (past tense bohte) "to buy, pay for, acquire; redeem, ransom; procure; get done," from Proto-Germanic *bugjan (source also of Old Saxon buggjan, Old Norse byggja, Gothic bugjan), which is of unknown origin and not found outside Germanic.

The surviving spelling is southwest England dialect; the word was generally pronounced in Old English and Middle English with a -dg- sound as "budge," or "bidge." Meaning "believe, accept as true" first recorded 1926. Related: Bought; buying. To buy time "prevent further deterioration but make no improvement" is attested from 1946.
buy (n.) Look up buy at Dictionary.com
"a purchase," especially a worthwhile one, 1879, American English, from buy (v.).
buy-in (v.) Look up buy-in at Dictionary.com
verbal phrase, "to purchase a commission or stock," 1826, from buy (v.) + in (adv.). As a noun by 1970.
buy-out (n.) Look up buy-out at Dictionary.com
also buy-out, "the purchasing of a controlling share in a company," 1976, from verbal phrase buy out "purchase someone's estate and turn him out of it," 1640s, from buy (v.) + out (adv.).
buyer (n.) Look up buyer at Dictionary.com
c. 1200, biggere "one who purchases," agent noun from buy (v.). Meaning "one whose job is to buy goods for a store" is from 1884. Buyer's market attested from 1886.
buzkashi (n.) Look up buzkashi at Dictionary.com
Afghan sport, a sort of mounted polo played with a goat carcass, 1956, from Persian buz "goat" + kashi "dragging, drawing."
buzz (v.) Look up buzz at Dictionary.com
late 15c., echoic of bees and other insects. Aviation sense of "fly low and close" is by 1941 (see buzz (n.)). Related: Buzzed; buzzing. Buzz off (1914) originally meant "to ring off on the telephone," from the use of buzzers to signal a call or message on old systems. As a command, it originally would have been telling someone to get off the line.
buzz (n.) Look up buzz at Dictionary.com
"a busy rumour" [Rowe], 1620s (earlier "a fancy," c. 1600), figurative use from buzz (v.). Literal sense of "humming sound" is from 1640s. A "buzz" was the characteristic sound of an airplane in early 20c.; hence verbal sense "to fly swiftly," by 1928; by 1940 especially in military use, "to fly low over a surface as a warning signal" (for example that target practice is about to begin):
The patrol aircraft shall employ the method of warning known as "buzzing" which consists of low flight by the airplane and repeated opening and closing of the throttle. [1941 Supplement to the Code of Federal Regulations of the United States of America," Chap. II, Corps of Engineers, War Department, p. 3434, etc. ]
Meaning "pleasant sense of intoxication" first recorded 1935. The children's game of counting off with 7 or multiples of it replaced by buzz is attested from 1864 and is mentioned in "Little Women" (1868). To give (someone) a buzz (by 1922) is from the buzz that announced a call on old telephone systems.
buzz-cut (n.) Look up buzz-cut at Dictionary.com
by 1973, American English, from buzz (n.), perhaps from the sound of the barber's electric clipper, + cut (n.) in the "haircut" sense.
buzz-saw (n.) Look up buzz-saw at Dictionary.com
1858, American English, from buzz (v.) + saw (n.).
buzzard (n.) Look up buzzard at Dictionary.com
c. 1300, from Old French buisart "buzzard, harrier, inferior hawk," from buson, buison, from Latin buteonem (nominative buteo) a kind of hawk, perhaps with -art suffix for one that carries on some action or possesses some quality, with derogatory connotation (see -ard).
buzzer (n.) Look up buzzer at Dictionary.com
c. 1600, "buzzing insect," agent noun from buzz (v.). In reference to mechanical devices that buzz, from 1870 (steam-powered at first; electric mechanisms so called from 1884).
buzzword (n.) Look up buzzword at Dictionary.com
also buzz word, 1946, from buzz (n.) + word (n.). Noted as Harvard student slang for the key words in a lecture or reading. Perhaps from the use of buzz in the popular counting game.
BVDs (n.) Look up BVDs at Dictionary.com
"men's underwear," 1935, from trademark name (dating to 1876) of manufacturer Bradley, Voorhees, and Day.
bwana Look up bwana at Dictionary.com
respectful or reverential form of address in East Africa, 1878, from Swahili.
by (prep.) Look up by at Dictionary.com
Old English be- (unstressed) or bi (stressed) "near, in, by, during, about," from Proto-Germanic *bi "around, about," in compounds often merely intensive (source also of Old Saxon and Old Frisian bi "by near," Middle Dutch bie, Dutch bij, German bei "by, at, near," Gothic bi "about"), from PIE *bhi, reduced form of root *ambhi- "around."

Originally an adverbial particle of place, in which sense it is retained in place names (Whitby, Grimsby, etc.). Elliptical use for "secondary course" (opposed to main, as in byway, also compare by-blow "illegitimate child," 1590s, Middle English loteby "a concubine," from obsolete lote "to lurk, lie hidden") was in Old English. This also is the sense of the second by in the phrase by the by (1610s). By the way literally means "in passing by" (mid-14c.); used figuratively to introduce a tangential observation by 1540s.

Phrase by and by (early 14c.) originally meant "one by one," modern sense is from 1520s. By and large (1660s) originally was nautical, "sailing to the wind and off it," hence "in one direction then another;" from nautical expression large wind, one that crosses the ship's line in a favorable direction.
by-product (n.) Look up by-product at Dictionary.com
also byproduct; 1857, from by + product.
Byblos Look up Byblos at Dictionary.com
ancient Phoenician port (modern Jebeil, Lebanon) from which Egyptian papyrus was exported to Greece. The name probably is a Greek corruption of Phoenician Gebhal, said to mean literally "frontier town" (compare Hebrew gebhul "frontier, boundary," Arabic jabal "mountain"), or perhaps it is Canaanite gubla "mountain." The Greek name also might have been influenced by, or come from, an Egyptian word for "papyrus."
bye (1) Look up bye at Dictionary.com
in sporting use, a variant of by (prep). Originally in cricket, "a run scored on a ball that is missed by the wicket-keeper" (1746); later, in other sports, "position of one who is left without a competitor when the rest have drawn pairs" (1883), originally in lawn-tennis.
bye (2) Look up bye at Dictionary.com
shortened form of good-bye. Reduplication bye-bye is recorded from 1709, though as a sound used to lull a child to sleep it is attested from 1630s.
bygone (adj.) Look up bygone at Dictionary.com
early 15c., from by (adv.) + gone. Compare similar construction of aforesaid. As a noun from 1560s (see bygones).
bygones (n.) Look up bygones at Dictionary.com
"things that are past," especially offenses, 1560s, from plural of noun use of bygone (q.v.).
bylaw (n.) Look up bylaw at Dictionary.com
late 13c., bilage "local ordinance," from Old Norse or Old Danish bi-lagu "town law," from byr "place where people dwell, town, village," from bua "to dwell" (from PIE root *bheue- "to be, exist, grow") + lagu "law" (see law). So, a local law pertaining to local residents, or rule of a corporation or association. Sense influenced by by.
byline (n.) Look up byline at Dictionary.com
1926, "line giving the name of the writer of an article in a newspaper or magazine;" it typically reads BY ________. From by (prep.) + line (n.). As a verb by 1958.
BYOB Look up BYOB at Dictionary.com
initialism (acronym) for "bring your own bottle" or "bring your own booze," by 1951.
bypass (v.) Look up bypass at Dictionary.com
1823, "to pass by" (implied in bypassed), from bypass (n.). From 1928 as "to go around, avoid;" figurative use from 1941. Related: Bypassed; bypassing.
bypass (n.) Look up bypass at Dictionary.com
also by-pass, 1848, of certain pipes in a gasworks, from the verbal phrase; see by + pass (v.). First used 1922 for "road for the relief of congestion;" figurative sense is from 1928. The heart operation was first so called 1957.
byre (n.) Look up byre at Dictionary.com
"cow-shed," Old English byre, perhaps related to bur "cottage, dwelling, house" (see bower).
Byronic (adj.) Look up Byronic at Dictionary.com
1823, pertaining to or resembling British poet George Gordon, 6th Baron Byron (1788-1824).
Perfect she was, but as perfection is
Insipid in this naughty world of ours,
Where our first parents never learn'd to kiss
Till they were exiled from their earlier bowers,
Where all was peace, and innocence, and bliss
(I wonder how they got through the twelve hours),
Don Jose like a lineal son of Eve,
Went plucking various fruit without her leave.

[from "Don Juan"]
bystander (n.) Look up bystander at Dictionary.com
1610s, from by + agent noun from stand (v.). They have been innocent at least since 1829. Stander-by is from 1540s.
byte (n.) Look up byte at Dictionary.com
1956, American English; see bit (n.2). Reputedly coined by Dr. Werner Buchholz at IBM.
byway (n.) Look up byway at Dictionary.com
mid-14c., from by + way (n.).