when i was a little my father told my that when you stare at people with your mouth open to be careful because a fly might fly into your mouth. I still do it as an adult because some people surprise and confuse me. It an awful expression although it shows exactly what your thinking.
A childhood belief about general

others believed things like this
- my brother told me that if i ride my bike with my mouth open i will swallow my tounge. Anon
- I used to think people had a "potty mouth" if they had been drinking out of the toilet.Anon
- I used to believe that if I slept with my mouth open that spiders would crawl in there and live in my stomachAnon
- I used to belive that if i put my foot in my mouth, I would get foot-and-mouth illness— Emily Sathrota
- I used to believe that the people who got shot in TV shows where people who wanted to die.Anon
- I used to believe that if you told a lie, Dragonflies will come and sew your mouth shut. For real.— Casey