I used to think that the Stone of Scone in Scotland was actually a giant scone that had been baked wrong and come out like hard rock. I thought that the scottish clans used to deliberately bake their scones like this to throw at their enemies - and this was where the term "sconning someone" came from. I believed this up until a year ago. I'm 24 now.
A childhood belief about history

others believed things like this
- I used to believe that scones were cone-shaped because the word is sCONES. — scone
- i used to think the sun was a giant fireball like the ones from the mario brothers throw except a big one.— chris
- when I was little I believed that if I put a white stone under the pillow with my tooth I make more moneyAnon
- i used to believe that the hard toe caps on rugby boots were made from giant ants found in the amazon!— eryll
- I used to think that roaches were aliens because it was hard to kill them. I'm still not so sure I was wrong.— Dev
- My friends and I used to believe that if you planted a rock, it would grow a rock tree. Anon