Etymology
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mole (n.1)

spot on skin, Old English mal "spot, mark, blemish," especially on cloth or linen, from Proto-Germanic *mailan "spot, mark" (source also of Old High German meil, German Mal, Gothic mail "wrinkle"), from PIE root *mai- (2) "to stain, soil, defile" (source also of Greek miainein "to stain, defile," see miasma). Specifically of small, permanent dark marks on human skin from late 14c.

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mole (n.2)

type of small burrowing insectivorous mammal (genus Talpa), mid-14c., molle (early 13c. in surnames); perhaps a shortening of obsolete moldwarp, literally "earth-thrower," but this sort of abbreviation is rare at that early age, and perhaps it is rather directly from the root of mold (n.3) "loose earth." It may represent an unrecorded Old English word; compare Middle Dutch mol, molle, Middle Low German mol, mul.

From c. 1600 as a figure of "one who works in darkness" (in Middle English, moldewerpe was figurative of a cleric overly concerned with worldly things). The espionage sense of "secret agent who gradually attains a position deep within organization or nation" was popularized 1974 in John le Carré (but suggested from early 20c.), from the notion of "burrowing."

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mole (n.3)

"massive structure used as a breakwater," 1540s, from French môle "breakwater" (16c.), ultimately from Latin moles "mass, massive structure, barrier," perhaps from PIE root *mō- "to exert oneself" (source also of Greek molos "effort," molis "hardly, scarcely;" German mühen "to tire," müde "weary, tired;" Russian majat' "to fatigue, exhaust," maja "hard work").

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mole (n.4)

unit of molecular quantity, 1902, from German Mol coined 1900 by German chemist Wilhelm Ostwald, short for Molekül (see molecule).

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moleskin (n.)

1660s, "the skin of a mole, used as fur," from mole (n.2) + skin (n.). From 1803 as the name of a kind of extra strong fustian.

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molar (adj.)

in chemistry, "pertaining to one mole of a substance," 1902, from mole (n.4) + -ar. Earlier it meant "pertaining to mass," from Latin moles "mass."

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molehill (n.)

also mole-hill, "mound or ridge of earth thrown up by moles in burrowing," mid-15c., from mole (n.2) + hill (n.). To make a mountain of a molehill "exaggerate an insignificant matter" is from 1560s.

To much amplifying thinges yt. be but small, makyng mountaines of Molehils. [John Foxe, "Acts and Monuments," 1570]
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molest (v.)

late 14c., molesten, "to cause trouble, grief, or vexation, disturb, harass," from Old French molester "to torment, trouble, bother" (12c.) and directly from Latin molestare "to disturb, trouble, annoy," from molestus "troublesome, annoying, unmanageable," which is perhaps related to moles "mass" (see mole (n.3)) on notion of either "burden" or "barrier." Meaning "sexually assault" is attested by 1950. Related: Molested; molesting.

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molecule (n.)

1794, "extremely minute particle," from French molécule (1670s), from Modern Latin molecula, diminutive of Latin moles "mass, barrier" (see mole (n.3)). For ending see -cule. It has a vague meaning at first; the vogue for the word (used until late 18c. only in Latin form) can be traced to the philosophy of Descartes. First used of Modern Latin molecula in modern scientific sense ("smallest part into which a substance can be divided without destroying its chemical character") is by Amedeo Avogadro (1811).

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demolish (v.)

1560s, "to destroy the structural character of (a building, wall, etc.), by violently pulling it to pieces," from French demoliss-, present-participle stem of démolir "to destroy, tear down" (late 14c.), from Latin demoliri "tear down," from de "down" (see de-) + moliri "build, construct," from moles (genitive molis) "massive structure" (see mole (n.3)). Figurative sense of "to destroy, lay waste" is from 1610s; humorously, "to consume," by 1756. Related: Demolished; demolishing.

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