When I was a kid, I thought that a pair of panty hose was plural - and that if you were only talking about one leg, it was a panty ho.
A childhood belief about speaking

others believed things like this
- i used to think that the word 'clothes' was the plural for 'clo.' so i'd call a sock or a shirt a clo. — jessimocha
- ... i used to believe the more stripes my pair of sneakers had, the faster i would run ...— wilbur
- Until about age 9, I thought there was a country called "Operaland" where everyone sang instead of talking.Anon
- When the police are talking about "rap sheets," I thought that the criminals were making rap music.Anon
- I used to believe the people of television were talking to me alone !— Margaux, a French student in eighth grade
- That people older than me knew what they were talking about.— Mark