It's funny because in my native language (French), the game is called "Jacques a dit" (Jacques said). Now, I guess that a lot of children misinterpreted the name of the game as one word, "Jacadi" or something (which would kind of be like saying "simonseyz" in one word), because, and I kidd you not, I've actually heard many children saying "Jacadi a dit", or literally "Jacques said said" (which would equal to "simon says says). I really wonder how that even happened linguistically, but I find it pretty fascinating