Etymology
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auto-focus (n.)

"device that focuses automatically," by 1933 in photography, originally of enlargers; by 1942 of lenses, from auto- + focus (n.).

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fylfot (n.)

supposedly a native name for the swastika (used as a decorative device), but only attested in a single, damaged c. 1500 manuscript, and in that it might rather refer to any sort of device used to fill the bottom (foot) of a design. "[I]t is even possible that it may have been a mere nonce-word" [OED].

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machine (v.)

mid-15c., "decide, resolve," from Old French and Latin usages, from Latin machina "machine, engine, military machine; device, trick; instrument," from Greek makhana, Doric variant of Attic mēkhanē "device, tool; contrivance, cunning" (see machine (n.)). Meaning "to apply machinery to, to make or form on or by the aid of a machine" is from 1878. Related: Machined; machining.

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door-stop (n.)

"device placed behind a door to prevent it from being opened too widely," 1859, from door + stop (n.).

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photometer (n.)

"instrument used to measure the intensity of light," 1778, from photo- "light" + -meter "device for measuring." Related: Photometric; photometry (1760).

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camera obscura (n.)

1725, "a darkened room;" c. 1730, "a device for project pictures;" see camera.

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humidifier (n.)

"device for making air more humid," by 1881, agent noun from humidify.

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pulser (n.)

by 1940, "device that gives electrical pulses," agent noun from pulse (v.).

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cloak-room (n.)

also cloakroom, 1827, "a room connected with an assembly-hall, opera-house, etc., where cloaks and other articles are temporarily deposited," from cloak (n.) + room (n.). Later extended to railway offices for temporary storage of luggage, and by mid-20c. sometimes a euphemism for "bathroom, lavatory."

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incinerator (n.)

"device for waste disposal by burning," 1872, from incinerate + Latinate agent noun suffix -or.

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