Etymology
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octahedron (n.)

"a solid figure bounded by eight plane faces," 1560s, from Greek oktahedron, neuter of oktahedros "eight-sided," from okta- "eight" (see octa-) + hedra "a seat; face of a geometrical solid," from PIE root *sed- (1) "to sit." Related: Octahedral.

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ersatz (adj.)
1875, from German Ersatz "units of the army reserve," literally "compensation, replacement, substitute," from ersetzen "to replace," from Old High German irsezzen, from ir-, unaccented variant of ur- (see ur-) + setzen "to set," from PIE root *sed- (1) "to sit." As a noun, from 1892.
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presidio (n.)

a seat of government, especially a place of military authority, hence, in U.S. Southwest, "a military post," 1808, American English, from Spanish presidio "fort, settlement," from Latin praesidium "defense, protection," from praesidere "to sit before, protect" (see preside). Related: Presidial; presidary.

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covey (n.)

mid-14c., "brood or flock of partridges" (also applied to similar birds), from Old French covee "a brood, a hatching" (Modern French couvée), from Gallo-Roman *cubata, literally "hatchling," from past-participle stem of Latin cubare "to sit, incubate, hatch" (see cubicle).

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brood (v.)
mid-15c., "sit on eggs for the purpose of hatching them," from brood (n.). The figurative meaning "meditate long and anxiously" (to "incubate in the mind") is first recorded 1570s, from notion of "nursing" one's anger, resentment, etc. Related: Brooded; brooding. Brood mare "female horse kept for breeding" is from 1829.
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resident (adj.)

late 14c., "dwelling, residing, having an abode in a place for a continuance of time," from Old French resident and directly from Latin residentem (nominative residens), present participle of residere "to sit down, settle" (see reside). From early 15c. as "stay in a place in discharge of some duty," originally ecclesiastical.

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polyhedron (n.)

"a solid bounded by many (usually more than 6) plane faces," 1560s, from Latinized form of Greek polyedron, neuter of adjective polyedros "having many bases or sides," from polys "many" (from PIE root *pele- (1) "to fill") + hedra "seat, base, chair, face of a geometric solid" (from PIE root *sed- (1) "to sit").

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tetrahedron (n.)
"triangular pyramid, solid figure contained by four triangular surfaces," 1560s, from Late Greek tetraedron, noun use of neuter of tetraedros (adj.) "four-sided," from tetra- "four" (from PIE root *kwetwer- "four") + hedra "seat, base, chair, face of a geometric solid," from PIE root *sed- (1) "to sit." Related: Tetrahedral.
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session (n.)

late 14c., sessioun, "periodical sitting of a court," from Old French session "act or state of sitting; assembly," from Latin sessionem (nominative sessio) "act of sitting; a seat; loitering; a session," noun of action from past-participle stem of sedere "to sit" (from PIE root *sed- (1) "to sit").

By 1550s in the general sense of "the time or term during which a legislature, etc. meets daily for business." The still more general sense of "period set aside for some activity" is recorded by 1920, in bull session, which probably is extended from quarter sessions courts (see quarter (n.1)).

The musical sense of "recording occasion in a studio" is from 1927. The literal classical sense has been rare in English except in theology, of Christ's enthronement at the right hand of the Father (early 15c.). Related: Sessional.

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Bundestag (n.)
German federal council, 1879, from German Bundestag, from genitive of Bund "league, confederacy, association" (related to English band (n.2) and bind (v.)) + tag, literally "day;" as a verb, tagen, "to sit in conference" (see day; also compare adjourn). Hence also Bundesrat "federal council of the German empire" (1872), from rat, rath "council" (see rathskeller).
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