gremlin n.

"small imaginary creature blamed for mechanical failures," oral use in R.A.F. aviators' slang from Malta, the Middle East and India is said to date to 1923. First printed use perhaps in poem in journal "Aeroplane" April 10, 1929; certainly in use by 1941, and popularized in World War II and picked up by Americans (for example New York Times Magazine April 11, 1943). Of unknown origin. OED says "probably formed by analogy with GOBLIN." Speculations in Barnhart are a possible dialectal survival of Old English gremman "to anger, vex" + the -lin of goblin; or Irish gruaimin "bad-tempered little fellow." Surfer slang for "young surfer, beach trouble-maker" is from 1961 (short form gremmie by 1962).