When I was little, my friend used the word "oxymoron." When I asked her what it meant, she said it was a horrible insult. I went around calling people oxymorons for a couple of years until someone finally told me what it really means!
A childhood belief about speaking

others believed things like this
- When I was a kid, I used to think that an oxymoron was a stupid ox.— Froogle
- I used to think that oxymoron had something to do with oxygen...Anon
- that the word "couple" as in "a couple of items" was synonymous with "several", rather than "just two".— Blair A. Petterson
- For years I heard the word "pedophile" and thought it meant a pedicurist's tool.— Lauren
- I fully believed, up until about 6 years old, that the word 'accident' was a noun that meant 'burnt toast'.— Karl Goetz
- I thought that "heck" was a less horrible version of hell for people who were only KIND OF evil.— Oizys