Gremlin

A gremlin is an imaginary creature commonly depicted as mischievous and mechanically oriented, with a specific interest in aircraft. Gremlins' mischievous natures are similar to those of English folkloric imps, while their inclination to damage or dismantle machinery is more modern.
Many people think that gremlins come from old myths, like leprechauns and pixies, but the gremlin was actually coined by the British Royal Air Force in the early 1900s. The word gremlin first appeared in print in a poem published in 1929 in the journal Aeroplane. Gremlin was used during WWII to explain the inexplicable mechanical problems that would happen while an aircraft was in flight. British author Roald Dahl, who served his military service in the Royal Air Force and was familiar with the concept of the gremlin, published a children's book that he called The Gremlins (1943). In it, he named the male gremlins widgets and the female gremlins fifinellas. In Gremlins the movie, the little furry creatures are called mogwai. 

Gremlin Mascot of 482nd Bomb Group

Origins
Although their origin is found in myths among airmen, claiming that the gremlins were responsible for sabotaging aircraft, John W. Hazen states that "some people" derive the name from the Old English word gremian, "to vex." Since the Second World War, different fantastical creatures have been referred to as gremlins, bearing varying degrees of resemblance to the originals.
The term "gremlin" denoting a mischievous creature that sabotages aircraft, originates in Royal Air Force (RAF) slang in the 1920s among the British pilots stationed in Malta, the Middle East and India, with the earliest recorded printed use being in a poem published in the journal Aeroplane, in Malta on April 10, 1929. Later sources have sometimes claimed that the concept goes back to World War I, but there is no print evidence of this.
An early reference to the Gremlin is in aviator Pauline Gower's The ATA: Women with Wings (1938) where Scotland is described as "gremlin country", a mystical and rugged territory where scissor-wielding gremlins cut the wires of biplanes when unsuspecting pilots were about. An article by Hubert Griffith in the servicemen's fortnightly Royal Air Force Journal dated April 18, 1942, also chronicles the appearance of gremlins,although the article states the stories had been in existence for several years, with later recollections of it having been told by Battle of Britain Spitfire pilots as early as 1940.
This concept of gremlins was popularized during the Second World War among airmen of the UK's RAF units, in particular the men of the high-altitude Photographic Reconnaissance Units (PRU) of RAF Benson, RAF Wick and RAF St Eval. The flight crews blamed gremlins for otherwise inexplicable accidents which sometimes occurred during their flights. Gremlins were also thought at one point to have enemy sympathies, but investigations revealed that enemy aircraft had similar and equally inexplicable mechanical problems. As such, gremlins were portrayed as being equal opportunity tricksters, taking no sides in the conflict, and acting out their mischief from their own self-interests. In reality, the gremlins were a form of "buck passing" or deflecting blame.This led the folklorist John Hazen to note, "Heretofore, the gremlin has been looked on as new phenomenon, a product of the machine age — the age of air."