I thought that "shit" was just a rude way of saying "stuff", rather than specifically meaning fecal matter, due to how people say things like "I don't have time for this shit."
A childhood belief about swearing

others believed things like this
- I used to believe that your arse cheeks were actually full of shit!Anon
- My sister used to think that "spit" was a bad word. She meant "shit".— "Spit!"
- i believed that michelle gayle's sweetness song contained the lyrics shade in sheep shit!— andrew
- I used to believe that some first names were specifically for children and some were specifically for adults.— Marco
- I used to believe that, no matter what language other people spoke, that everyone thought in EnglishAnon
- I held my breath near cemeteries because I thought it would be rude to inhale spirits. Anon