You are absolutely right, this amazing movie directed by Joe Dante and written by Chris Columbus (who also wrote The Goonies!! and Home Alone), is truly a unique masterpiece and except for the name of the creatures, Roald Dahl had nothing to do with it. I just wanted to point out how Roald came up with things that affected modern pop culture, however, it seems that Roald only brought the term to pop-culture, he never invented it. Here are some interesting facts I found about the movie:
"Unbeknownst to Joe Dante and Michael Finnell, Steven Spielberg was a big fan of "The Howling" (1981). After he came across Chris Columbus' writing sample, he fell in love with it and bought it. Then he decided that Dante was the guy to make it into a movie, took the project to Warner Bros. and also produced it with his own company, Amblin Entertainment."
"The original Gremlins script was much, much darker. Case in point: Earlier scenes included the Gremlins eating Billy’s dog then decapitating his mom and throwing her head down the stairs. Spielberg, director Joe Dante, and Warner Bros. were all in agreement that they should tone down the gore in order to make the movie more family-friendly."
"The idea for these creatures was born in a loft in Manhattan's garment district that was home to NYU Film School graduate screenwriter Chris Columbus. "By day, it was pleasant enough, but at night, what sounded like a platoon of mice would come out and to hear them skittering around in the blackness was really creepy." Columbus recalls."
"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."