I used to believe that "Oldsmobile" was a universal name for any old, big, rusty car. When I was some impressionable young age and just old enough to figure out how compound words worked, my father owned an old, big, rusty Oldsmobile. I concluded that "Oldsmobile" must mean "old + mobile."
Imagine my surprise when a few years later, he bought a new Oldsmobile that was not a rustbucket.
A childhood belief about cars

others believed things like this
- when I was young, I heard that blood had iron in it. I thought blood was red because it was rusty.— Hunter
- I used to wander what my name would be in other languages. I thought that names worked the same way as words. — Simon
- At a young age I couldn't imagine how people without glasses could marry the ones wearing them. — Ana
- i beleived that when someone bought a new house, they would swap with the person they bought it from— c
- I used to beleive in stores that were open 24/7 , that the people that worked there worked 24/7 nonstop.Anon
- I used to belive that employees who worked at 24/7 shops lived there and never slept!(they worked 24/7)— tilly Waukesha WI