Until I was 16 and I had my first PROPER girlfriend, I always assumed the vaginal opening would be on the front of the pelvis, because that's where the penis is.
Imagine my confusion when I found it's actually tucked underneath.
Also, when I started masturbation, I knew it was frowned open, so instead I used to have sex with the bed in what I called "sex practice."
A childhood belief about rude bits

others believed things like this
- My girlfriend belived that sitcoms were called that because you sat down to watch them.— Zeppy
- We use to think the male organ (penis) was called a PUDDLE....
My twin sister and I both called it that...Anon - Up until I was about 14, I always thought that the penis was called a "pickle."— Amanda
- I used to believe that a penis was called a bobby because my mum told me... I believed this until I was 15.— Patricia
- That masturbation would make you blind— NN
- I thought that the show Beavis and Butthead was called Penis and Butthead.— Porky's Butthole