1917, noun, verb, and adjective, from French camoufler, Parisian slang, "to disguise," from Italian camuffare "to disguise," which is of uncertain origin, perhaps a contraction of capo muffare "to muffle the head." Probably altered in French by influence of French camouflet "puff of smoke, smoke puffed into a sleeper's face" (itself of unknown origin) on the notion of "blow smoke in someone's face." The British navy in World War I called it dazzle-painting.
Since the war started the POPULAR SCIENCE MONTHLY has published photographs of big British and French field pieces covered with shrubbery, railway trains "painted out" of the landscape, and all kinds of devices to hide the guns, trains, and the roads from the eyes of enemy aircraft.
Until recently there was no one word in any language to explain this war trick. Sometimes a whole paragraph was required to explain this military practice. Hereafter one word, a French word, will save all this needless writing and reading. Camouflage is the new word, and it means "fooling the enemy." [Popular Science Monthly, August 1917]
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.
Old armies spent winters in quarters and took to the "open field" to seek battle in summer. Generalized to "continued or sustained aggressive operations for the accomplishment of some purpose" (1790); in U.S., especially "political activity before an election, marked by organized action in influencing the voters" [DAE], attested from 1809.