My mother told me "that's where the indian shot you". This must be a saying of sorts possibly from an old western.
A childhood belief about belly buttons

others believed things like this
- My dad told me when I was little that my belly button was "Where the Indian shot me"Anon
- I used to believe that guns shot out blood because everytime somebody shot a gun in a movie you saw blood.Anon
- When I was younger, I thought that Labour Day was when all sorts of women gave birth.— Greg
- I used to think Indian women had scabs on their foreheads, but it was bindi!— Emily
- I thought that Indian Summer was like the weather in India.Anon
- I used to believe that those of Indian descent who had them were born with dots on their forehead.Anon