Online Etymology Dictionary

bell (v.): "attach a bell to," late 14c., from bell (n.). Related: Belled; belling. Allusions to the story of the mice that bell the cat (so they can hear him coming) date to 1520s.
bell-bottoms (n.): type of trousers, 1882, from bell (n.) + bottom (n.). Distinguished in the late 1960s from flares by the shape of the expanded part (flares straight, bell-bottoms curved).
Bella: fem. proper name, from Italian bella "fair," from Latin bella, fem. of bellus "beautiful, fair" (see bene-). In some cases short for Isabella (see Isabel).
belladonna (n.): 1590s, "deadly nightshade" (Atropa belladonna), from Italian, literally "fair lady;" the plant so called supposedly because women made cosmetic eye-drops from its juice (an 18c. explanation; atropic acid, found in the plant, has a well-known property of dilating the pupils) or because it was used to poison beautiful women. Perhaps a folk etymology alteration; Gamillscheg suggests ultimately of Gaulish origin.
Bellatrix: bright star in the left shoulder of Orion, from Latin bellatrix "female warrior," frequently used as an adjective, "warlike, skilled in war," fem. of bellator "to wage war," from bellum "war" (see bellicose). The Latin name, from the Alfonsine Tables (mid-13c.), very loosely translates the Arabic name for the star, Al Najid "the conqueror."
In astrology it was the natal star of all destined to great civil or military honors, and rendered women born under its influence lucky and loquacious; or as old Thomas Hood said, "Women born under this constellation shall have mighty tongues." [Allen]
bellboy (n.): from bell (n.) + boy; originally (1851) a ship's bell-ringer, later (1861) a hotel page.
belle (n.): "beautiful woman well-dressed; reigning beauty," 1620s, from French belle, from Old French bele, from Latin bella, fem. of bellus "beautiful, fair" (see bene-).
Bellerophon: Greek hero, from Latin form of Greek Bellerophontes, probably literally "killer of (the demon) Bellerus," from -phontes "killer of."
belles-lettres (n.): "elegant literature, aesthetics," 1710, French, literally "fine letters," from belles, plural of belle, fem. of beau "fine, beautiful" (see beau) + lettres, plural of lettre "letter" (see letter (n.)). The literary equivalent of beaux arts.
belletrist (n.): also bellettrist, 1816, an awkward contraction of belles-lettres + -ist. Adjective belletristic is recorded from 1821.
bellhop (n.): also bell-hop, by 1906, American English, shortening of slang bellhopper (1899), from bell (n.) + hop (v.). The notion is one who "hops" into action when the bell is rung.
bellicose (adj.): early 15c., "warlike," from Latin bellicosus "warlike, valorous, given to fighting," from bellicus "of war," from bellum "war," Old Latin duellum, dvellum, which is of uncertain origin.
bellicosity (n.): 1840, from bellicose + -ity.
bellied (adj.): having a swelling or hollow middle, late 15c., from belly (n.). Also, in compounds, "having a belly" (of a certain kind).
belligerence (n.): 1804; see belligerent + -ence. Related: belligerency. Middle English had belligeration "warfare."
belligerent (adj.): 1570s, from Latin belligerantem (nominative belligerans), past participle of belligerare "to wage war," from bellum "war" (see bellicose) + gerere "to bear, to carry" (see gest). The noun meaning "party or nation at war" is from 1811. Related: Belligerently.
Bellona: Roman goddess of war, from Latin bellum "war," Old Latin duellum, dvellum, which is of uncertain origin.
bellow (v.): apparently from Old English bylgan "to bellow," from PIE root *bhel- (4) "to sound, roar." Originally of animals, especially cows and bulls; used of human beings since c. 1600. Related: Bellowed; bellowing. As a noun from 1779.
bellowing (n.): late 14c., from present participle of bellow (v.). As an adjective, recorded from 1610s.
bellows (n.): c. 1200, belwes, "a bellows," literally "bags," plural of belu, belw, northern form of beli, from late Old English belg "bag, purse, leathern bottle" (see belly (n.)). Reduced from blæstbælg, literally "blowing bag." Used exclusively in plural since 15c., probably due to the two handles or halves.
bellwether (n.): mid-14c. (late 13c. in Anglo-Latin; late 12c. as a surname), from bell (n.) + wether; the lead sheep (on whose neck a bell was hung) of a domesticated flock. Figurative sense of "chief, leader" is from mid-14c.
belly (v.): "to swell out," 1620s, from belly (n.). Related: Bellied; bellying. Old English belgan meant "to be or become angry" (a figurative sense). A comparable Greek verb-from-noun, gastrizein, meant "to hit (someone) in the belly."
belly (n.): Old English belg, bylig (West Saxon), bælg (Anglian) "leather bag, purse, bellows," from Proto-Germanic *balgiz "bag" (source also of Old Norse belgr "bag, bellows," bylgja "billow," Gothic balgs "wineskin"), from PIE *bholgh-, from root *bhelgh- "to swell," an extension of *bhel- (2) "to blow, swell" (see bole). Meaning shifted to "abdomen of a human or animal" (late 13c.) as the old plural form of the noun emerged as a separate word (see bellows). Meaning "bulging part or convex surface of anything" is 1590s. The West Germanic root had a figurative or extended sense of "anger, arrogance" (as in Old English bolgenmod "enraged;" belgan (v.) "to become angry"), probably from the notion of "swelling."

Indo-European languages commonly use the same word for both the external belly and the internal (stomach, womb, etc.), but the distinction of external and internal is somewhat present in English belly/stomach; Greek gastr- (see gastric) in classical language denoted the paunch or belly, while modern science uses it only in reference to the stomach as an organ.

As a personal name from 12c. From c. 1200 as a symbol of gluttony. Belly-naked in Middle English was "stripped to the belly, completely naked." Fastidious avoidance of belly in speech and writing (compensated for by stretching the senses of imported stomach and abdomen, baby-talk tummy and misappropriated midriff) began late 18c. and the word was banished from Bibles in many early 19c. editions. Belly-punch (n.) is attested from 1811.
belly button (n.): "navel," 1877, colloquial, from belly (n.) + button (n.). Also bellybutton, belly-button.
belly dance (n.): also bellydance, 1883, from belly (n.) + dance (n.), in later uses translating French danse du ventre. As a verb from 1963.
bellyache (n.): also belly-ache, 1590s, from belly (n.) + ache (n.). The verb in the slang sense of "complain" is first recorded 1888, American English; it appears not to have been used earlier than that, if ever, in a literal sense. Related: bellyached; bellyaching.
bellyful (n.): figuratively, "enough and more," 1530s, from belly (n.) + -ful. Older than the literal sense (1570s).
belong (v.): mid-14c., "to go along with, properly relate to," from be- intensive prefix, + longen "to go," from Old English langian "pertain to, to go along with," which is of unknown origin. Senses of "be the property of" and "be a member of" first recorded late 14c. Cognate with Middle Dutch belanghen, Dutch belangen, German belangen. Replaced earlier Old English gelang, with completive prefix ge-.
belongings (n.): "goods, effects, possessions," 1817, from plural of verbal noun from belong.
beloved (adj.): late 14c., from past participle of verb belove (c. 1200), from be- + loven "to love" (see love (v.)). Noun meaning "one who is beloved" is from 1520s.
below (adv.): early 14c., biloogh, from be- "by, about" + logh, lou, lowe "low" (see low (adj.)). Apparently a variant of earlier a-lowe (influenced by other adverbs in be-; see before), the parallel form to an-high (now on high). Beneath was the usual word; below was very rare in Middle English and gained currency only in 16c. It is frequent in Shakespeare. As a preposition from 1570s. According to Fowler, below is the opposite of above and concerns difference of level and suggests comparison of independent things. Under is the opposite of over and is concerned with superposition and subjection and suggests some interrelation.
Belshazzar: last Chaldean king of Babylon (Dan. v), from Hebrew Belshatztzar, a contraction of Akkadian Bel-shar-usur, literally "Bel-protect-the-king" (see Bel).
belt (n.): Old English belt "belt, girdle," from Proto-Germanic *baltjaz (source also of Old High German balz, Old Norse balti, Swedish bälte), an early Germanic borrowing from Latin balteus "girdle, sword belt," said by Varro to be an Etruscan word.

As a mark of rank or distinction, mid-14c.; references to boxing championship belts date from 1812. Mechanical sense is from 1795. Transferred sense of "broad stripe encircling something" is from 1660s. Below the belt "unfair" (1889) is from pugilism. To get something under (one's) belt is to get it into one's stomach. To tighten (one's) belt "endure privation" is from 1887.
belt (v.): early 14c., "to fasten or gird with a belt," from belt (n.). Meaning "to thrash as with a belt" is 1640s; general sense of "to hit, thrash" is attested from 1838. Colloquial meaning "to sing or speak vigorously" is from 1949. Related: Belted; belting. Hence (from the "thrash with a belt" sense) the noun meaning "a blow or stroke" (1899).
Beltane (n.): early 15c., from Lowland Scottish, from Gaelic bealltainn "May 1," important Celtic religious rite marking the start of summer, probably literally "blazing fire," from PIE root *bhel- (1) "to shine, flash, burn" (see bleach (v.)) + Old Irish ten "fire," from PIE *tepnos, related to Latin tepidus "warm." But this derivation of the second element is hotly disputed by some on philological grounds, and fires were equally important in the other Celtic holidays.
The rubbish about Baal, Bel, Belus imported into the word from the Old Testament and classical antiquity, is outside the scope of scientific etymology. [OED]
Also known as "Old May Day," because after the 1752 calendar reform it continued to be reckoned according to Old Style; it was one of the quarter-days of ancient Scotland.
beltless (adj.): 1884, from belt (n.) + -less.
beltway (n.): term in U.S. for a ring highway around an urban area, especially Interstate 495 around Washington, D.C., the Capital Beltway, completed 1964; from belt (n.) + way (n.). Figurative for "Washington, D.C., and its culture" for better or worse, since c. 1978.
beluga (n.): 1590s, from Russian beluga, literally "great white," from belo- "white" (from PIE *bhel-o-, from root *bhel- (1) "to shine, flash, burn;" see bleach (v.)) + augmentative suffix -uga. Originally the great sturgeon, found in the Caspian and Black seas; later (1817) also the small white whale (Delphinapterus leucas) found in northern seas.
belvedere (n.): "raised turret atop a house," 1590s, from Italian belvedere, literally "a fair sight," from bel, bello "beautiful" (from Latin bellus "beautiful, fair;" see bene-) + vedere "a view, sight" (see vista). Pronunciation perhaps influenced by the French form of the word. So called because it was used for viewing the grounds.
Bembo (n.): type face, 1930; the type was cut in 1929 based on one used in 15c. by Aldus Manutius in an edition of a work by Pietro Bembo.
bemoan (v.): Old English bemænan "to bemoan, wail, lament;" see be- + moan (v.). Related: Bemoaned; bemoaning.
bemuse (v.): "to make utterly confused," from be- + muse (compare amuse); attested from 1735 but probably older, as Pope (1705) punned on it as "devoted utterly to the Muses."
bemused (adj.): 1735, past participle adjective from bemuse (v.). Related: Bemusedly.
bemusement (n.): 1881, from bemuse + -ment.
ben (n.): "mountain peak" in Celtic place names (especially of roughly pyramidal peaks standing alone), from Gaelic beinn, from Old Irish *benno- "peak, horn, conical point," from PIE root *bend- "projecting point."
bench (n.): Old English benc "long seat," from Proto-Germanic *bankiz "bank of earth," perhaps here "man-made earthwork," later "bench, table" (source also of Old Frisian bank "bench," Old Norse bekkr, Danish bænk, Middle Dutch banc, Old High German banch), from PIE root *bheg- "to break." Used for "office of a judge" since late 13c. Sporting sense "reserve of players" (in baseball, North American football, etc.) is by 1909, from literal sense of place where players sit when not in action (by 1889).
bench (v.): "to take out of the game," 1902, from bench (n.) in the sporting sense. Related: Benched; benching. Old English also had a verb form, but it meant "to make benches."
bench-warmer (n.): 1892, baseball slang; see bench.
The days for "bench-warmers" with salaries are also past. ["New York Sporting News," Jan. 9, 1892]
Old English had bencsittend "one who sits on a bench."
benchmark (n.): also bench-mark, "surveyor's point of reference," 1838, from a specialized surveyors' use of bench (n.) + mark (n.1); figurative sense is from 1884.
bend (v.): Old English bendan "to bend a bow; confine with a string, fetter," causative of bindan "to bind," from Proto-Germanic base *band- "string, band" (source also of Old Norse benda "to join, strain, strive, bend"), from PIE root *bhendh- "to bind" (source also of Gothic bindan, Old High German bintan, Sanskrit badhnati "binds," Lithuanian bendras "partner;" Old Persian bandaka- "subject").

Modern sense (early 14c.) is via notion of bending a bow to string it. Cognate with band, bind, and bond. Related: Bended; bent; bending.