Etymology
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bulk (n.)
mid-15c., "a heap; the volume or bulk of something," earlier "ship's cargo" (mid-14c.), from a Scandinavian source akin to Old Norse bulki "a heap; ship's cargo," from Proto-Germanic *bul-, from PIE root *bhel- (2) "to blow, swell."

Meaning extended by early confusion with obsolete bouk "belly" (from Old English buc "body, belly," from Proto-Germanic *bukaz; see bucket), which led to sense of "size, volume, magnitude of material substance," attested from mid-15c. In bulk 1670s, "loaded loose." Meaning "the greater part" (of anything) is by 1711.
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B.T.U. 

1889 as an abbreviation of British Thermal Unit (1862), a commercial unit of electrical energy (the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit); the French Thermal Unit is the amount of heat required to raise 1 kilogram of water 1 degree centigrade. Also from 1889 as an abbreviation of Board of Trade Unit, in electicity "1,000 watt hours."

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span (n.1)
"distance between two objects," from Old English span "distance between the thumb and little finger of an extended hand" (as a measure of length, roughly nine inches), probably related to Middle Dutch spannen "to join, fasten," from Proto-Germanic *spannan, from PIE root *(s)pen- "to draw, stretch, spin."

The Germanic word was borrowed into Medieval Latin as spannus, hence Italian spanna, Old French espan "hand's width, span as a unit of measure," French empan. As a measure of volume (early 14c.), "what can be held in two cupped hands." Meaning "length of time" first attested 1590s; that of "space between abutments of an arch, etc." is from 1725. Meaning "maximum lateral dimension of an aircraft" is first recorded 1909.
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monad (n.)

1610s, "unity, arithmetical unit," 1610s, from Late Latin monas (genitive monadis), from Greek monas "unit," from monos "alone" (from PIE root *men- (4) "small, isolated"). In Leibnitz's philosophy, "an ultimate unit of being, a unit of the universal substance" (1748); he apparently adopted the word from Giordano Bruno's 16c. metaphysics, where it referred to a hypothetical primary indivisible substance at once material and spiritual. Related: Monadic; monadism.

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Euro (n.)
name for the basic monetary unit of a pan-European currency, from 1996.
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festschrift (n.)
"volume of writings by various scholars presented as a tribute or memorial to a veteran scholar," 1898, from German Festschrift, literally "festival writing" (see -fest + script (n.)).
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sone (n.)

unit of loudness, 1936, from Latin sonus "sound," from PIE root *swen- "to sound."

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picosecond (n.)

unit of time equal to one trillionth of a second, 1966, from pico- + second (n.).

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megavolt (n.)

unit of measure equivalent to one million volts, 1868, from mega- "one million" + volt.

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lira (n.)
Italian monetary unit, 1610s, from Italian lira, literally "pound," from Latin libra "pound (unit of weight);" see Libra, and compare livre. There also was a Turkish lira.
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