I used to believe that "Hazchem" was a German word meaning "danger" (hence the signs up at factories etc).
I was 21 before I figured out, all by myself at least, that it was an abbreviation for "hazardous chemicals".
A childhood belief about foreign languages

others believed things like this
- My little brother once asked my mother when we past a couple of factories.. if the factories made clouds— nicky
- i used to believe that the factories were care bear factories because of the clouds of smogAnon
- I used to think you had to be an adult to drink household chemicalsAnon
- Having seen enough red octagonal STOP signs in my time, I used to look out for green circular GO signs.— Gary
- I used to think that the abbreviation lb (for pounds) stood for Lilla-blams (like Kilograms)— Jake
- I used to believe that clouds came from the smoke that came from the factories. — Anela