Etymology
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troop (n.)

1540s, "body of soldiers," 1540s, from French troupe, from Old French trope "band of people, company, troop, crowd" (13c.), a word of uncertain origin, perhaps from Frankish *throp "assembly, gathering of people" or another Germanic source, perhaps related to Old English ðorp, Old Norse thorp "village" (see thorp). OED derives the French word from Latin troppus "flock," which is of unknown origin but also might be from the proposed Germanic source. Of groups of animals from 1580s. Specifically as "a subdivision of a cavalry force" from 1580s; of Boy Scouts from 1908. Troops "armed forces" is from 1590s.

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movement (n.)

late 14c., mevement, "change of position; passage from place to place," from Old French movement "movement, exercise; start, instigation" (Modern French mouvement), from Medieval Latin movimentum, from Latin movere "to move, set in motion" (from PIE root *meue- "to push away"). In the musical sense of "major division of a piece" it is attested from 1776; in the political/artistic/social sense of "course of acts and endeavors by a body of persons toward some specific end" is from 1828. Related: Movements.

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troop (v.)
1560s, "to assemble," from troop (n.). Meaning "to march" is recorded from 1590s; that of "to go in great numbers, to flock" is from c. 1600. Related: Trooped; trooping.
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Brownian movement (n.)
"rapid oscillatory motion observed in very small particles," 1850, for Scottish scientist Dr. Robert Brown (1773-1858), who first described it.
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trooper (n.)
1630s, "soldier in a cavalry troop," from troop (n.) + -er (1). Extended to "mounted policeman" (1858, in Australia) then to "state policeman" (U.S.) by 1911.
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paratroops (n.)

"body of soldiers who are dropped by parachute into enemy territory," 1940, from parachute + plural of troop (n.).

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chetnik (n.)
"member of a Balkan guerrilla force," 1904, from Serbian četnik, from četa "band, troop."
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condottiere (n.)

"professional leader of a mercenary troop," 1794, from Italian condottiere, from condotto "to conduct," from Latin conducere "to lead or bring together" (see conduce).

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Hanse (n.)
also Hansa, medieval merchants' guild, late 12c. in Anglo-Latin, via Old French hanse and Medieval Latin hansa, both from Middle Low German hanse "fellowship, merchants' guild," from Old High German hansa "military troop, band, company." This is related to Gothic hansa "troop, company, multitude," Old English hos "attendants, retinue." A member was a Hansard. Compare Hanseatic.
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troupe (n.)
1825, "company, band," especially of performers, actors, dancers, etc., from French troupe "company" (see troop (n.)).
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