Etymology
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ethno- 
word-forming element meaning "race, culture," from Greek ethnos "people, nation, class, caste, tribe; a number of people accustomed to live together" (see ethnic). Used to form modern compounds in the social sciences.
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classless (adj.)

1874 in the social sense, "having or belonging to no class," from class (n.) in the "social order" sense + -less. As "lacking the sophistication of high class," by 1979. Related: Classlessly; classlessness.

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ideo- 
word-forming element variously used with reference to images or to ideas, from Greek idea "form; the look of a thing; a kind, sort, nature; mode, fashion," in logic, "a class, kind, sort, species" (see idea).
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classify (v.)

"arrange in a class or classes, arrange according to common characteristics," 1782, from French classifier, from classe (see class (n.)) + -fier (see -fy). Related: Classified; classifying.

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classroom (n.)

also class-room, "room in which school lessons are taught," 1811, from class (n.) + room (n.).

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crustacean (n.)

an animal of the class Crustacea, 1835; see Crustacea + -an. As an adjective, "of or pertaining to an animal of the class Crustacea," 1858 (an earlier adjective was crustaceous, "pertaining to crust, crust-like," 1640s).

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occlusion (n.)

"act or fact of being stopped up," 1640s, from Medieval Latin occlusionem (nominative occlusio), noun of action from past-participle stem of Latin occludere (see occlude). Dentistry sense "position of the two sets of teeth relative to each other when the mouth is closed" is from 1880.

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hum (v.)
late 14c., hommen "make a murmuring sound to cover embarrassment," later hummen "to buzz, drone" (early 15c.), probably of imitative origin. Sense of "sing with closed lips" is first attested late 15c.; that of "be busy and active" is 1884, perhaps on analogy of a beehive. Related: Hummed.
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box-turtle (n.)
1825, American English for what is called by English writers a box-tortoise (1834), from box (n.1), so called for its resemblance to a tight, closed box when the head, tail, and legs are drawn in.
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dentiloquy (n.)

"act or practice of speaking through the teeth or with the teeth closed," 1737, from Latin dens (genitive dentis) "tooth" (from PIE root *dent- "tooth") + -loquy, from Latin loqui "to speak" (from PIE root *tolkw- "to speak"). Related: Dentiloquist.

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