Etymology
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flask (n.)
mid-14c., from Medieval Latin flasco "container, bottle," from Late Latin flasconem (nominative flasco) "bottle," which is of uncertain origin. A word common to Germanic and Romanic, but it is unclear whether the Latin or Germanic word is the original (or whether both might have got it from the Celts). Those who support a Germanic origin compare Old English flasce "flask, bottle" (which would have become modern English *flash), Old High German flaska, Middle Dutch flasce, German Flasche "bottle." If it is Germanic, the original sense might be "bottle plaited round, case bottle" (compare Old High German flechtan "to weave," Old English fleohtan "to braid, plait"), from Proto-Germanic base *fleh- (see flax).

Another theory traces the Late Latin word to a metathesis of Latin vasculum. "The assumption that the word is of Teut[onic] origin is chronologically legitimate, and presents no difficulty exc[ept] the absence of any satisfactory etymology" [OED]. The similar words in Finnish and Slavic are held to be from Germanic.
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powder (n.)

 "fine, minute, loose, uncompacted particles," c. 1300, poudre, "ash, cinders; dust of the earth;" early 14c. of any pulverized substance; from Old French poudre "dust, powder; ashes; powdered substance" (13c.), earlier pouldre (11c.), from Latin pulverem (nominative pulvis) "dust, powder" (source also of Spanish polvo, Italian polve; see pulverize).

The insertion of the unetymological -d- was common in French (compare meddle, tender (adj.), remainder). German has it as a doublet; Puder via French and Pulver from Latin. From mid-14c. specifically as "medicinal powder;" specialized sense of "gunpowder" is from late 14c. In the sense "powdered cosmetic," it is recorded from 1570s.

Powder keg "small barrel for holding gunpowder" is by 1820; the figurative sense ("something likely to explode easily") is by 1895. Powder room, euphemistic for "women's lavatory," is attested from 1936. Earlier it meant "place where gunpowder is stored on a warship" (1620s). Powder monkey "boy employed on ships to carry powder from the magazines to the guns" is from 1680s. Powder blue (1650s) was smalt used in laundering; as a color name from 1894.

The phrase take a powder "scram, vanish," is from 1920; it was a common phrase as a doctor's instruction, so perhaps the notion is of taking a laxative medicine or a sleeping powder, with the result that one has to leave in a hurry (or, on another guess, from a magician's magical powder, which makes things disappear).

Avis dropped an exhausted little heap onto her aunt's bed. She put her hand over her heart and said piteously, "Oh, Aunt Joyce, I mustn't ever do that again. My heart's going awful fast. I shall have to take a powder. Wasn't it fun though-" Avis' dark eyes flashed. [from "The Evolution of Avis" in The Connecticut School Journal, Jan. 9, 1902]
When the wife of your breast has confessed she has drest
   On just triple the sum you allowed her,
And has run up long bills for her frocks and her frills—
   Take a powder, my friend, take a powder.
[from "The Panacaea," in Punch, Dec. 14, 1901]

Powder in the wind (c. 1300, meaning powdered spices) was a Middle English image of something highly valued but flawed in some way that renders it impermanent or doomed to loss (of virtues without humility, etc.).

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powder (v.)

c. 1300, poudren, "to put or sprinkle powder on;" late 14c., "to make into powder," from Old French poudrer "to pound, crush to powder; strew, scatter," from poudre (see powder (n.)). Specifically as "to whiten cosmetically by some application of white material in powder form" is from 1590s. Related: Powdered; powdering.

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powder-puff (n.)

1704, "small feathery ball (of swansdown, etc.) for applying powder to the skin," from powder (n.) + puff (n.). As a symbol of femaleness or effeminacy, by 1930s. 

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powder-horn (n.)

"powder flask made of horn (usually of an ox or cow) with a movable stopper at the small end," 1530s, from powder (n.) + horn (n.). 

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ampoule (n.)
"small bottle or flask," especially one used for holy liquids, c. 1200, from Old French ampole "flask, vial," from Latin ampulla "small globular flask or bottle," which is of uncertain origin, perhaps a contracted form of amphora. Superseded in English by the form ampulla and later ampul.
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flagon (n.)

"large bottle for wine or liquor," mid-15c., from Old French flacon, flascon "small bottle, flask" (14c.), from Late Latin flasconem (nominative flasco) "bottle" (see flask).

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powdery (adj.)

"of the nature or consistency of powder," early 15c., poudri, from powder (n.) + -y (2).

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kohl (n.)
"powder used to darken the eyelids, etc.," properly of finely ground antimony, 1799, from Arabic kuhl (see alcohol).
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compact (n.2)

"small make-up case," 1919, from compact (adj.), based on its containing compacted face powder.

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