Green’s Dictionary of Slang

an unidentified source of trouble or malfunctioning.

1929		Aeroplane 10 Apr. 57: All officers below the rank of Squadron Leader [...] They are but a herd of gremlins, / Gremlins who do all the flying, / Gremlins who do much instructing.
1941		(con. 1910s) C. Graves Thin Blue Line 123: As he flew round, he wished that his instructor had never told him about the Little People a mythological bunch of good and bad fairies originally invented by the Royal Naval Air Service in the Great War [...] Those awful little people, the Gremlins, who run up and down the wing with scissors going ‘snip, snap, snip’ made him sweat .
1943		Smith & Carnes American Guerrilla 208: They were all brand-new. It could not be helped [...] For rough, tough desert going I would greatly have preferred trucks which had been taken over the jumps a few times, the wrinkles ironed out and the gremlins under control .
1944		‘Words and the War’ AS XIX 280: Gremlins are mythical creatures who are supposed to cause trouble such as engine failure in aeroplanes, a curious piece of whimsy-whamsy in an activity so severely practical as flying. Now the gremlin seems to be extending its sphere of operations, so that the term can be applied to almost anything that inexplicably goes wrong in human affairs.
1945		‘Song of the Gremlins’ in Mess Songs & Rhymes of the RAAF 43: Oh, it’s then that you see the Gremlins, / Green, Gamboge and Gold, / Male, female and neuter,/ Gremlins both young and old.
1962		H. Livings Nil Carborundum (1963) Act III: Friggin gremlins.
1971		A. Buzo The Roy Murphy Show (1973) 103 : How about a dry run, Col? Get rid of the gremlins.
1999		Observer 18 July 29: Gremlins afflicted the complex test manoeuvrings and dockings of Apollos 8, 9 and 10.