When I was young I used to read a comic called The Dandy.
One strip was called the Jocks & The Geordies.
It was easy to see that the Jocks were Scots because they wore big Tam O' Shanters & liked to say stuff like "Jings" when they were surprised.
The Geordies all wore smart school uniforms & spoke plain English, so I assumed they were posh English kids & Geordie was a Scottish slang word for such a person.
My Dad was surprised when I started to use Geordie in this context & had to explain it actually meant someone from Newcastle, which is a fairly unposh place.
A childhood belief about nationalities

others believed things like this
- At the age of four I believed I was soooo smart. I spoke TWO languages...English AND American!— Melinda
- I used to think that even people who spoke something other than English, thought in English— Peaches
- I used to think that adults spoke an entirely different language (not English) when kids weren't around. — Swordfish
- I used to believe that the numbers athletes wore on their uniforms were their ages.— Sara
- I used to believe that people who wore glasses were very smart.— Anonymous
- I used to belief that the Muslim women who wore their garment wore it because they were bald.Anon