For years I didn't realise that "soccer" was football (i.e. English Association football). I thought the word was pronounced "sosser", and for some reason thought it was a game like throwing a frisbee.
A childhood belief about sport

others believed things like this
- When I was little, I used to believe that football players really had shoulders that big.— Angie
- I used to believe that a football ref's flag was a banana peel.Anon
- When I was a kid, I used to think that the only way you could play football was if you had giant shoulders.— Sam
- I used to think that the Hunchback of Notre Dame was a football player.— Wendy
- I used to believe that a hat trick in football was achieved when a player scored a goal with their head!— Andy
- I thought that soccer moms were moms that played soccer!Anon