I used to believe that when someone "ate out" a girl they would actually eat food out of the girls private part.
A childhood belief about oral sex

others believed things like this
- When I was a little girl I thought that if you put salt on your food it cooled it off! lol What — Darlene
- When I was a little girl, I believed that all cats were girls and all dogs were boys. :)— Mary Ellen
- I used to think it was true that only ugly girls poop and I thought I was an ugly girl because I poopedAnon
- I used to believe that grilled cheese was called 'girl cheese,' and only girls could eat it.— Paige
- I used to believe that boys had boy babies, and girls had girl babies.
That was when I was 3-7. I'm 15 now.— Stefanie Michelle - When I was a child, I used to believe that armpits were private parts— Duda Gueiros