I used to believe the word 'lack' meant lots of something. I'd say things like "we sure have a lack of pepsi here!", and adults thought I had learned sarcasm.
A childhood belief about speaking

others believed things like this
- When I was 10, I thought that nausea was called Lack-O-Candy Disease. My mom made it up— Teddybearhaha
- I Used To Believe That GayNess Came From Lack Of Confidence In Ones Appearance— Mr Payne
- When I saw signs stating "Lots for sale" I thought it meant that there was a lot for sale.— Robin
- I used to believe that "nuptial" was a naughty word. I thought it meant nipple. XD— Sara Hagen
- For years I heard the word "pedophile" and thought it meant a pedicurist's tool.— Lauren
- when I was little, I called coke and pepsi "Black Juice"— can I have a refil on the black juice?