Etymology
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concentration (n.)

1630s, "action of bringing to a center, act of collecting or combining into or about a central point," noun of action from concentrate (v.). Meaning "a mass so collected" is from 1670s; that of "voluntary continuous focusing of mental activity" is from 1825, in phrenology.

Concentration camp is from 1901, originally "compound for noncombatants in a war zone," a controversial idea in the second Boer War (1899-1902). The term emerged with a bad odor.

The concentration camp has now definitely taken its place side by side with the Black Hole of Calcutta as one of those names of horror at which humanity will never cease to shudder. [The Review of Reviews, London, March 1902]

But it also was used 1902 in reference to then-current U.S. policies in the Philippines, and retroactively in reference to Spanish policies in Cuba during the 1896-98 insurrection there. The phrase was used domestically in the U.S. during the Spanish-American war but only in reference to designated rendezvous points for troops headed overseas. In reference to prisons for dissidents and minorities in Nazi Germany from 1934, in Soviet Russia from 1935. 

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camp (v.)
"to encamp, establish or make a camp," 1540s, from camp (n.). Related: Camped; camping. Later "to live temporarily in tents or rude places of shelter" (1610s), in modern times often for health or pleasure. Camping out is attested from 1834, American English.
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camp (n.)

1520s, "place where an army lodges temporarily," from French camp, in this sense from Italian campo, from Latin campus "open field, level space," especially "open space for military exercise" (see campus).

The direct descendant of Latin campus in French is champ "a field." The Latin word had been taken up in early West Germanic as *kampo-z and appeared originally in Old English as camp "contest, battle, fight, war." This word was obsolete by mid-15c.

Transferred to non-military senses by 1550s. Meaning "body of adherents of a doctrine or cause" is from 1871. Camp-follower "one who follows an army without being officially connected to it," such as sutlers, washer-women, etc., first attested 1810. Camp-meeting "religious meeting for prayer, etc., held in an outdoor camp" is from 1809, American English, originally and especially in reference to Methodists. Camp-fever (1758) is any epidemic fever incident to life in a camp, especially typhus or typhoid. A camp-stool (1794) has a flexible seat and cross-legs and is made to be folded up and packed away when not in use.

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camp (adj.)
"tasteless," 1909, homosexual slang, of uncertain origin, perhaps from mid-17c. French camper "to portray, pose" (as in se camper "put oneself in a bold, provocative pose"); popularized 1964 by Susan Sontag's essay "Notes on Camp." Campy is attested from 1959.
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camp-ground (n.)
also campground, "place for camping," 1806, from camp (n.) or (v.) + ground (n.).
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Camp David 
U.S. presidential retreat near Thurmont, Maryland, built 1939 as Hi-Catoctin, in reference to the name of the mountains around it; called Shangri-La by F.D. Roosevelt, after the mythical hard-to-get-to land in the novel "Lost Horizon;" named Camp David by Eisenhower in 1953 for his grandson, born 1947. The Camp David Accords were signed there Sept. 17, 1978.
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death camp (n.)

1944, in reference to the Holocaust, probably translating German Todeslager; they also were known as extermination camps (German Vernichtungslager); historians usually count six of them: Auschwitz-Birkenau, Chełmno, Bełżec, Majdanek, Sobibór, Treblinka.

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boot camp (n.)
"training station for recruits," by 1941, U.S. Marines slang, said to be from boot (n.1) as slang for "recruit," which is attested by 1915 and supposedly dates from the Spanish-American War and is a synecdoche from boots "leggings worn by U.S. sailors."
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Dachau 

town in Bavaria, Germany, from Old High German daha "clay" + ouwa "island," describing its situation on high ground by the Amper River. Infamous as the site of a Nazi concentration camp nearby, opened in 1933 as a detention site for political prisoners and surrendered to the U.S. Army April 29, 1945.

Not a death camp, but as it was one of the places where inmates from other camps were sent as the Reich collapsed at the end of the war, and as it was one of the few large camps overrun by British or American forces, in the West it came to symbolize Nazi atrocities. "Arbeit Macht Frei" was spelled out in metal on the gate (as it was on other camps, such as Gross-Rosen, Sachsenhausen, Theresienstadt).

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encampment (n.)
1590s, "place where a camp is formed," from encamp + -ment. From 1680s as "act of forming a camp."
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