I used to believe that sticking up your middle finger meant 'I hate you', something we weren't ever allowed to say in our house. So when I was feeling naughty, I would stick my middle finger up at dilapidated old houses from the backseat of the car as we drove by (and then feel horribly guilty).
A childhood belief about swearing

others believed things like this
- I used to believe that a half moon was gods finger nail, and his finger was pointing downwards.— clo
- my brother (10) still believes that if you stick your finger to far up your nose you can touch your brainAnon
- I used to think that "No standing signs" meant that you weren't allowed to actually stand in the area!Anon
- Never point at a grave, if you do your finger will rot off.— KL.R
- I used to believe that if my finger was ever cut off, it would grow back.— Chrissy
- i used to believe that if i bit my fingernails then a finger would grow in my stomach— polly