Etymology
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Mercury 

"the Roman god Mercury," herald and ambassador of his father, Jupiter, mid-12c., Mercurie, from Latin Mercurius "Mercury," originally a god of tradesmen and thieves, from merx "merchandise" (see market (n.)); or perhaps [Klein, Tucker] from Etruscan and influenced by merx. De Vaan thinks it possible the whole stem *merk- was borrowed and the god-name with it.

Mercury later was identified with Greek Hermes and still later with Germanic Woden. From his role as a messenger and conveyor of information, since mid-17c. Mercury has been a common name for a newspaper. 

The planet closest to the sun was so called in classical Latin (c. 1300 in English). A hypothetical inhabitant of the planet was a Mercurean (1855) or a Mercurian (1755). For the metallic element, see mercury.

In U.S. numismatics, the Mercury-head dime (so called by 1941) was in circulation from 1916; properly it is the female head of Liberty, in her characteristic cap, here winged to symbolize freedom of thought. But the resemblance to Mercury was noted in coin circles at once, and the coin design sometimes was popularly mistaken as the head of Mercury, Roman god of making money and thieving, in his winged hat. It was so-called in 1933 in newspaper articles calling attention to the fasces on the reverse. The coin is more correctly the Winged Liberty-head dime (simple Liberty-head dime being a designation of the previous design). The design was replaced in 1946, which made it necessary for it to have an agreed-upon specifying name.

There's the four-year-old who counted out 20 cents with the remark: "A boy dime and a girl dime."
Translated, this means a Roosevelt dime and one classified by coin books as the "new Mercury head" dime.
[Dothan Eagle, June 25, 1951]
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mercury (n.)

silver-white fluid metallic element, late 14c., from Medieval Latin mercurius, from Latin Mercurius (see Mercury). Prepared in ancient times from cinnabar, it was one of the seven metals (bodies terrestrial) known to the ancients, which were coupled in astrology and alchemy with the seven known heavenly bodies. This one probably was associated with the planet for its mobility. The others were Sun/gold, Moon/silver, Mars/iron, Saturn/lead, Jupiter/tin, Venus/copper.

The Greek name for it was hydrargyros "liquid silver," which gives the element its symbol, Hg. Compare quicksilver, which is its popular name. It has a freezing point of -39° C. The use of the word in reference to temperature or state of the atmosphere (by 1756) is from its use in thermometers and barometers.

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mercuric (adj.)

1828, in chemistry, "relating to or containing mercury," from mercury + -ic. Specifically applied to compounds in which each atom of mercury is regarded as bivalent. Mercurous (1840) is applied to those in which two atoms of mercury are regarded as forming a bivalent radical.

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mercurial (adj.)

late 14c., "pertaining to or under the influence of the planet Mercury," from Latin Mercurialis, from Mercurius (see Mercury). Meaning "pertaining to the god Mercury, having the form or qualities attributed to Mercury" (in reference to his role as god of trade or as herald and guide) is from 1590s. Meaning "light-hearted, sprightly, volatile, changeable, quick" (1640s) is from the qualities supposed to characterize those born under the planet Mercury (they also are the qualities of the god Mercury), probably also partly by association with the qualities of quicksilver. A variant in this sense was mercurious (1590s). Related: Mercurially; mercuriality.

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intramercurial (adj.)
"being within the orbit of the planet Mercury," 1859, especially in reference to a supposed planet orbiting there (sought in vain in the eclipse of 1860), from intra- "within, inside" + Mercury (Latin Mercurius) + -al (1). The idea originated in France in the 1840s with Urbain Le Verrier, who later became director of the Paris Observatory. There was some excitement about it in 1859 when a French doctor named Lescarbault claimed to have tracked it crossing the Sun's disk and convinced Le Verrier. It was sought in vain in the solar eclipses of 1860, '68, and '69. See Vulcan.
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amalgamation (n.)
1610s, "act of compounding mercury with another metal," noun of action from archaic amalgam (v.) "to alloy with mercury" (see amalgamate). Figurative, non-chemical sense of "a combining of different things into one uniform whole" is attested from 1775. Especially of the union or merger of corporations under one direction.
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amalgamize (v.)
1590s, "reduce to a soft mass by combination with mercury," from amalgam + -ize. Related: Amalgamized; amalgamizing.
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amalgam (n.)
c. 1400, "a blend of mercury with another metal; soft mass formed by chemical manipulation," from Old French amalgame or directly from Medieval Latin amalgama, "alloy of mercury (especially with gold or silver)," c. 1300, an alchemists' word, probably from Arabic al-malgham "an emollient poultice or unguent for sores (especially warm)" [Francis Johnson, "A Dictionary of Persian, Arabic, and English"], which is itself perhaps from Greek malagma "softening substance," from malassein "to soften," from malakos "soft" (from PIE *meldh-, from root *mel- (1) "soft"). Figurative meaning "compound of different things" is from 1790.
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talaria (n.)
"winged sandals of Hermes (Mercury)" and often other gods (Iris, Eros, the Fates and the Furies), 1590s, from Latin talaria, noun use of neuter plural of talaris "of the ankle," from talus "ankle" (see talus (n.1)).
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hydrargyrum (n.)
"mercury, quicksilver," 1560s, from Latin hydrargyrus, from Greek hydrargyros "quicksilver" (as prepared artificially from cinnabar ore; native quicksilver was argyros khytos "fused silver"), from hydr-, stem of hydor "water" (from suffixed form of PIE root *wed- (1) "water; wet") + argyros "silver" (from PIE root *arg- "to shine; white," hence "silver" as the shining or white metal). Hence the chemical abbreviation Hg for the element mercury.
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