The first time I ever learned the word "diarrhea", it was in a context that didn't make the specific meaning clear. Instead I got the idea that diarrhea meant any poop. I thought I'd learned the "grown up" term for poop, and started saying "I have diarrhea" any time I needed to poop. After a while, my mother got concerned and took me to the doctor. I don't remember what, if anything, was resolved there. And it seems it must have been years later that my confusion finally got cleared up as to what exactly diarrhea is.
A childhood belief about weeing and pooing

others believed things like this
- My nephew (age 7) thought tampons were plugs for diarrhea. Anon
- I actually asked my mother if mixing girls' poop and boys' poop would cause an explosion.— kraine
- My poop was always around the same color as my skin so I assumed white people's poop was white.— jaycee
- when I was little I used to think that white people had pink poop (i am brown so my poop is brown)— helena muteka
- I used to believe that if you had a pee AND a poop at exactly the same time, then you would die— ange
- I used to beleive that eggs were actually poop from chickens, and that eating it would make you throw up.Anon