What is a "cliché" in movies that people like to reference, that doesn't actually happen in movies?
Discussion
(piefed.social)
This article in The Guardian suggests a story where the butler did it earlier than that - The Strange Case of Mr Challoner in 1921.
Even so "the butler did it" is still a great example of a cliché that hardly ever actually happens.
I could easily believe the cliché originated independently from any particular book, purely as a piece of writing advice meaning "don't be obvious!"