I used to believe the word firefighters was actually "firefire" because they sound similar.
I knew they put out fires, because that is why they would be called firefires. Their job is about fire.
A childhood belief about spelling

others believed things like this
- I thought firefighters were really "firefires," and burned houses down insted of putting them out.Anon
- I used to believe that the Fire Station was where all fires occurred.Anon
- I used to believe that firemen drove around in their fire trucks and started fires. I wondered why.— Albert
- I use to believe the sound that a car made when it was running low on gas was what they called horse power...— Bianca
- i used to believe the sound from a piano came from the keys hitting a stuff called "sploosh"{wierd, huh?}.— exploding buttox
- I thought that hot water couldn't put out fires.— Matt