I used to think that a "Wet Fart" or "Shart" (fart with a little more to it) was called a "Wet Birdie".
It wasn't until late in highschool I found out that it was just my family who called it that because I made it up when I was very little.
A childhood belief about farting

others believed things like this
- I was about 6 and thought my family invented the fart because I never heard anyone outside my family do it.— Bob
- I used to believe that my grandpa had a special power that made him fart each time I pulled his finger. — confused
- I used to believe if you fart hard enough you can fly— Bob
- I used to believe that when you fart, your tummy was breathing!— Nicholas Orsmond
- i used to believe that if i swallowed gum i would fart a bubble— jeremy
- i used to believe that if you didnt fart that you would throw your guts upAnon