I used to believe that when someone on a swing was "going crooked" they were "going cricket." I spent several years telling my friends they were "going cricket" on the swings before coming to the realization that I was using the wrong word.
A childhood belief about speaking

others believed things like this
- I used to believe that Jiminy Cricket was a grasshopper because I had never seen a green cricket.Anon
- I forgot the expression "not cricket", so I said, "not tennis" instead.Anon
- I used to believe that cricket ice cream used to be made out of real crickets!!!— Lt. Fuzz
- I used to think that swing music was called that because you listened to it when playing on the swing set.Anon
- That if you went on the swings right after you ate, you would get chicken pox.Anon
- I used to wonder why they didn't fix the Leaning Tower Of Pisa. Weren't they embarrassed that it was crooked?— Bootlebat