also back-scratcher, "rod or other device for scratching one's own back," 1834; see back (n.) + scratch (v.).

"device for removing humidity from the air," 1909, agent noun from dehumidify (1908); see de- + humidify.

"device for catching and retaining," especially "a fastening for a door," late 13c., probably from latch (v.).

"device giving a signal about some physical activity," 1947, from a shortened form of sensory (q.v.) or an agent noun in Latin form from sense (v.).

"instrument for measuring the forces of gravity," 1797, from French gravimètre, from gravité (see gravity) + -mètre "measuring device" (see -meter).

"machine for separating cotton from seeds," 1796, American English, used earlier of other machineries, especially of war or torture, from Middle English gin "ingenious device, contrivance" (c. 1200), from Old French gin "machine, device, scheme," shortened form of engin (see engine). The verb in this sense is recorded from 1789. Related: Ginned; ginning. Middle English had ginful "ingenious, crafty; guileful, treacherous" (c. 1300).

"device for connecting computers and electronic musical instruments," 1983, acronym for Musical Instrument Digital Interface.

also fly-wheel, "heavy-rimmed revolving wheel to regulate motion," 1784, from fly (n.) "speed-regulating device" (1590s, from fly (v.1)) + wheel (n.).

also switch-board, "device for making interchangeable connections between many circuits," 1867, from switch (n.) + board (n.1).

1838, in hydraulics, "device for filtering impurities from water," from sand (n.) + trap (n.). As "golf bunker," by 1906.