1917, from air (n.1) + force (n.); first attested with creation of the Royal Air Force. There was no United States Air Force until after World War II. The Air Corps was an arm of the U.S. Army. In 1942, the War Department reorganized it and renamed it Army Air Forces. The National Security Act of 1947 created the Department of the Air Force, headed by a Secretary of the Air Force, and the U.S.A.F.

1917, shortened form of ammunition.

also auto-pilot, 1917, originally in airplanes, from auto- + pilot (n.). The figurative use (of persons, behaviors) is by 1996.

"pertaining to traditional Hindu science of medicine," 1917, from Sanskrit Ayurveda "science of life," from ayur "life" (from PIE *oyus-, suffixed form of *oyu- "life everlasting," from variant form of root *aiw- "vital force, life; long life, eternity") + veda "knowledge" (see Veda).

"traitor," 1917, from Paul Bolo, French adventurer shot for treason April 17, 1918; used in World War I with reference to pacifist propagandists; later somewhat assimilated to Bolshevik (q.v.).

"Russian radical socialist of the revolutionary period," 1917, from Russian bol'shevik (plural bol'sheviki), from bol'shiy "greater," comparative of adjective bol'shoy "big, great" (as in Bolshoi Ballet), from Old Church Slavonic boljiji "larger," from PIE root *bel- "strong" (source also of Sanskrit balam "strength, force," Greek beltion "better," Phrygian balaios "big, fast," Old Irish odbal "strong," Welsh balch "proud;" Middle Dutch, Low German, Frisian pal "strong, firm").

The faction of the Russian Social Democratic Worker's Party after a split in 1903 that was either "larger" or "more extreme" (or both) than the Mensheviks (from Russian men'shij "less"); after they seized power in 1917, the name was applied generally in English to Russian communists, then also to anyone opposed to an existing order or social system. Bolshevism is recorded from 1917.

1917, noun, verb, and adjective, from French camoufler, in Parisian slang, "to disguise," from Italian camuffare "to disguise," which is of uncertain origin, perhaps a contraction of capo muffare "to muffle the head." The word was 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]

cigar-shaped tubes of fried pastry filled with a sweet cheese or cream, a Sicilian dessert, 1917, from Italian cannoli, plural of cannolo, from cannola, literally "small tube," from Latin cannula "small reed or pipe," diminutive of canna "reed, pipe" (see cane (n.)). 

"body louse," 1917, British World War I slang, earlier in nautical use, said to be from Malay (Austronesian) kutu, the name of some parasitic, biting insect.

originally "body lice," 1917, see cootie.