Etymology
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Words related to *dwo-

anadiplosis (n.)

in rhetoric, "repetition at the start of a line or phrase of the last word or words of the preceding one," 1580s, from Latin, from Greek anadiplosis, from anadiploesthai "to be doubled back, to be made double," from ana "back" (see ana-) + diploun "to double, fold over" (see diploma).

Fear leads to anger. Anger leads to hate. Hate leads to suffering. [Yoda, "Star Wars"]
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balance (n.)

early 13c., "scales, apparatus for weighing by comparison of mass," from Old French balance "balance, scales for weighing" (12c.), also in figurative sense; from Medieval Latin bilancia, from Late Latin bilanx, from Latin (libra) bilanx "(scale) having two pans," possibly from Latin bis "twice" (from PIE root *dwo- "two") + lanx "dish, plate, scale of a balance," which is of uncertain origin.

The accounting sense "arithmetical difference between the two sides of an account" is from 1580s; meaning "sum necessary to balance the two sides of an account" is from 1620s. Meaning "what remains or is left over" is by 1788, originally in commercial slang. Sense of "physical equipoise" is from 1660s; the meaning "general harmony between parts" is from 1732.

Many figurative uses are from Middle English image of the scales in the hands of personified Justice, Fortune, Fate, etc.; thus in (the) balance "at risk, in jeopardy or danger" (c. 1300). Balance of power in the geopolitical sense "distribution of forces among nations so that one may not dominate another" is from 1701. Balance of trade "difference between the value of exports from a country and the value of imports into it" is from 1660s.

barouche (n.)

type of large, four-wheeled carriage, 1801, from dialectal German barutsche, from Italian baroccio "chariot," originally "two-wheeled car," from Latin birotus "two-wheeled," from bi- "two" (from PIE root *dwo- "two") + rotus "wheel," from rotare "go around" (see rotary). Frenchified in English, but the word is not French.

The half-top, for morning and evening drives, is much liked: the top being thrown down, the carriage presents an elegant appearance, and affords an opportunity for the display of full dress—hence it is popular with visitors at watering places and public parks. [Henry William Herbert ("Frank Forester"), "Hints to Horse-Keepers," New York, 1859]
between (prep., adv.)

Old English betweonum, Mercian betwinum, "in the space which separates, midway, in the midst, among; by turns," from bi- "by" (see by) + tweonum dative plural of *tweon "two each" (compare Gothic tweih-nai "two each;" from PIE root *dwo- "two").

Between is literally applicable only to two objects; but it may be and commonly is used of more than two where they are spoken of distributively, or so that they can be thought of as divided into two parts or categories, or with reference to the action or being of each individually as compared with that of any other or all the others. When more than two objects are spoken of collectively or in divisibly, among is the proper word. [Century Dictionary]

In all senses, between has been from its earliest appearance, extended to more than two. [OED]

Between a rock and a hard place "caught in a dilemma, in a difficult situation" is from 1940s, originally cowboy slang (earlier was between the beetle (hammer) and the block, late 19c.). Between-whiles "at intervals" is from 1670s. 

betwixt (prep., adv.)
Old English betweox "between, in the space that separates, among, amidst, meanwhile," from bi- "by" (see by) + tweox "for two," from Proto-Germanic *twa "two" (from PIE root *dwo- "two") + *-isk "-ish." With unetymological -t that first appeared in Old English and became general after c. 1500. Compare amidst. Betwixen also was a variant in Old and Middle English.
bezel (n.)
1610s, "slope of the edge of a cutting tool," also "groove by which a stone is held in its setting," from Old French *besel (13c.; Modern French biseau), cognate with Spanish and Portuguese bisel; of uncertain origin, perhaps literally "a stone with two angles," from Vulgar Latin *bis-alus, from bis- "twice" (from PIE root *dwo- "two") + ala "wing, side" (see alar). Meaning "oblique face of a gem" is from c. 1840. The verb meaning "grind (a tool) down to an edge" is from 1670s. Compare bevel.
bi- 
word-forming element meaning "two, having two, twice, double, doubly, twofold, once every two," etc., from Latin bi- "twice, double," from Old Latin dvi- (cognate with Sanskrit dvi-, Greek di-, dis-, Old English twi-, German zwei- "twice, double"), from PIE root *dwo- "two."

Nativized from 16c. Occasionally bin- before vowels; this form originated in French, not Latin, and might be partly based on or influenced by Latin bini "twofold" (see binary). In chemical terms, it denotes two parts or equivalents of the substance referred to. Cognate with twi- and di- (1).
binary (adj.)
"dual, twofold, double," mid-15c., from Late Latin binarius "consisting of two," from bini "twofold, two apiece, two-by-two" (used especially of matched things), from bis "double" (from PIE root *dwo- "two"). Binary code in computer terminology was in use by 1952, though the idea itself is ancient. Binary star in astronomy is from 1802.
bis- 
word-forming element meaning "twice," from Latin bis "twice, in two ways, doubly," from Old Latin dvis, cognate with Sanskrit dvih, Avestan bish, Greek dis, Middle High German zwis "twice," from PIE root *dwo- "two." Also the form of bi- used before -s-, -c-, or a vowel.
biscuit (n.)
respelled early 19c. from bisket (16c.), ultimately (besquite, early 14c.) from Old French bescuit "biscuit" (12c.), altered under influence of cognate Old Italian biscotto, both from Medieval Latin biscoctum, literally "twice-baked," from Latin (panis) bis coctus "(bread) twice-baked;" see bis- + cook (v.). Originally a kind of hard, dry bread baked in thin cakes; U.S. sense of "small, round soft bun" is recorded from 1818.