I couldn't understand why no-one had invented a word for something that isn't big but at the same time isn't small so I used to express the concept with the word "little-big" or "big-little". It was a revelation to me when my mother asked me go to the shops for a medium sliced loaf (of bread) and I discovered that someone somewhere had actually solved the problem that was perplexing me at the time.
A childhood belief about speaking

others believed things like this
- "Better than sliced bread"
I used to believe 'Sliced Bread' was a musical band.— Madeline - I used to think small furniture shops were basically cottage converted charity shops.Anon
- I used to believe that greyhounds chssed after a loaf of bread.Anon
- I used to believe that I actually invented the word "excellent".— poop jacket
- Up until 8th grade or so, I was convinced that I invented the word "Fart"— Jonah
- I used to think that "boobies" was a bad word all the timeAnon