When I was four years old my big brother and sister taught me the horrible swear word 'flabbergasted' and delighted in my saying it over and over. Then they told me they were going to tell Mom that I had been swearing, but convinced me the best option would be for me to tell on myself. Which I did.
33 years later they still bring that one up.
A childhood belief about swearing

others believed things like this
- I used to believe that swearing was just saying, “I swear!”Anon
- i used to think the word "suck" was a swear wordAnon
- I used to believe that bizarre was a swear word.Anon
- I used to believe that “shut up” was a swear word.Anon
- i used to believe that if you said a swear word you would turn into the opposite sex the next day— jess
- My cousin used to think that "body" was a swear word.— Jordan