When I was little, I spent a brief period of time for reasons I don't remember under the impression that to "swear" meant to tell lies at school.
A childhood belief about swearing

others believed things like this
- I used to think that the song "My Bonnie Lies Over the Ocean" was really "My Body Lies Over the Ocean."Anon
- When I was at primary school I thought you had to be at least 18 to swear.— Mike W
- i could swear eleventeen was a number for the longest time -- it still sounds pretty convincing.— erin
- When I was in elementary school nuns cam to our school. I thought that 'nun' meant they had no religion.Anon
- I thought that your period came out all at once and you had to wear a pad around the time it would come.— Sarah
- If you had a mouth ulcer it's because you've been telling lies.— David Smithers