At around the age of 7-9 I somehow came to the belief that the abbreviation "lb." for pound was actually an abbreviation for the unit of measure "lillebeeter". Perhaps I'd mis-heard the word "millimeter", which was still a relative rarity in 70's Canada?
A childhood belief about reading

others believed things like this
- I used to think that the abbreviation lb (for pounds) stood for Lilla-blams (like Kilograms)— Jake
- I used to believe that your soul was a millimeter thick, right under your skin, and looked exactly like youAnon
- In first grade, I thought that if I've never heard of a word before, then it wasn't a word.— Destiny
- When I was young, I heard the word 'minion' for the first time and thought it was a miniature onion.— Karin
- For years I heard the word "pedophile" and thought it meant a pedicurist's tool.— Lauren
- I used to believe that The Mall Of America was in Canada. — Adam