I had a friend growing up, and her parents used to talk about "Sumbees". These, apparently, were very bad people.
I was always puzzled by this, until they told the story that when she was about 18 months old, she was looking through her coloring book, and every time she couldn't get the page to turn smoothly, she'd exclaim, "Sumbee!"
It took them several times of seeing this to figure out she was saying, "Sonofabitch!". (If you're not British, and you've never heard a Texan pronounce this word, it comes out as "Sum-bitch!".
A childhood belief about swearing

others believed things like this
- I used to pronounce the word "Computer" as "Crocuta"
Anon - I used to beleive condoms were pills, until I saw an outline of one in a book about growing up, EWW!— Condoms r pills... right?
- i thought that we were just a big story book that ended when we died— samantha
- When I was young, I heard the word 'minion' for the first time and thought it was a miniature onion.— Karin
- My younger sibling thought that Brittany was the name of the country where British people livedAnon
- there's such thing as "soul-security"( social security )
because of the way my stupid parents pronounce it— elizabeth