I use to beleive that because oui (which sounds exactly like wee) mean yes in french, that poo meant no.
A childhood belief about foreign languages

others believed things like this
- When I was young I thought that police had soft skin, because this is how it sounds in French " Peau lisse "
— amine - I used to believe that french kiss was something coming from France, and that only the French did it— Sasha
- I used to think that you had to be french to really taste french fries.— Not French;)
- I used to beleive that if you point at a graveyard, it would point back!!(whatever that meant)— scary ashley
- i used to think that french was english backwards!— ---pepsi---
- I used to believe that french fries were made of bread.— tendersoul