My parents used to make me (and still want me) to say "butter" instead of butt.
My babysitter used to make her kids say "shoot a bunny" instead of fart, and my parents adopted that phrase for my sister and I a while, until they realized it might not be such a good thing for vegetarians to say.
In kindergarten, I used to point with my middle finger, but my teacher told me to stop. I asked why, but I don't think she ever told me.
A childhood belief about swearing

others believed things like this
- When I was younger I asked my parents:
"If bees make honey, do flys make marmalade?"— Mike - When I was a kid My friend’s mom told me if I swallowed my bubblegum it would make me fart bubblegum bubblesAnon
- My mother told me if I ate too much butter I'd get worms. I didn't eat too much butter...— Dicky
- I thought that barf was what they used to make peanut butter and jelly sandwiches!— Maan o' War
- i used to believe that parents do things to make there children happier. well i was wrong. — Emma C.
- When I was little, I thought you had to put a finger under the water to make it hot. — M_2