I thought the saying "run amok" was actually "run a muck" and figured a "muck" must be some weird measurement of distance I had never heard of!
A childhood belief about speaking

others believed things like this
- I thought common as muck was a substance called commoners muck— oddsox
- I used to believe a mile was the distance between telephone poles.— Allegra
- Airplanes got places faster because it was actually a shorter distance up there.Anon
- whenever i heard a melody, i thought it stuck in my stomach when i heard it in my mindAnon
- haha... i was around six or seven... i thought that mosquitoes grew into flies... weird..— ?!
- Until just a few seconds ago, I thought gherkins were beans or something weird like natto...Anon