Gremlins were a legend of the British Royal Air Force, and were described by Roald Dahl in his children's book The Gremlins.
The Gremlins were little mischief-making creatures who caused problems for the RAF: bullet holes in the wings of your plane might not have been made by German bullets, but by Gremlins! They help the pilots, too, warning them of disaster.
Originally Gremlins lived in a lovely forest, but their home was destroyed by an airplane factory. They went to live in the airplanes -- with special boots that let them walk upside-down and cling to the surface of the plane. Female gremlins are called Fifinellas; boys are Widgets and girls are Flipperty-Gibbets.
Dahl was a close friend of U.S. President Roosevelt; Eleanor Roosevelt read the Gremlin stories in manuscript to her grandchildren. The British Information Service -- a propaganda unit -- passed the story on to Disney, who bought the rights and started making a Gremlin movie in 1942. To promote interest in the film, they got a short version of the story published in Cosmopolitan magazine, and the full length book was published soon after. The film was never released.
The book was more or less a flop and Dahl considered it an embarrassment; it wasn't reprinted.
The 1984 movie had almost nothing to do with Dahl's concept!