I didn't know I a separate orifice for my urethra until I was 12. I always had thought that my urethra emptied urine into my vagina and then exitted my body.
Also, I didn't know what my "private parts" were called until I was 6 years old. How unfair. My brother had a penis, but my whatever-it-was had no name. Then it took me a few years to sort out the difference between a vulva and a vagina
A childhood belief about rude bits

others believed things like this
- i used to believe that a penis was the same as a vagina except really long— *stupid*
- i used to believe that if you have sex for too long, the penis would stay in your vagina— Angela
- i used to think that having sex was licking the persons vagina or penis until u got tiredAnon
- I used to think that Aretha Franklin's name was Urethra Franklin. Anon
- When I was a child, I used to believe that armpits were private parts— Duda Gueiros
- Until I was ten or eleven I thought a vagina was a "pagina" Anon