Whem my kids were young, we lived on a hobby farm. So they were familiar with the rubber rings we affixed around the male lambs' scrotums to castrate them. When my oldest boy was about 10, he found a rolled-up, unused condom and asked what it was. We had to tell him that it was used to stop people from having babies. He put two and two together and figured it worked just like those rubber rings we used on the lambs.
A childhood belief about condoms

others believed things like this
- I didn't mind eating lambs brains when I was a kid because I thought it would make me smart.Anon
- I thought family jewels were heirloom rings.— Care Bear
- When I was a kid I loved to eat onion rings, until I realized that they were made with onions.— Beth Pärssinen
- I used to believed that the children borned by tucking the finger info nunptial rings!!!— Silvia Mazzei
- I had an 18 lb. cat who ate rubber bands, I used to believe she could bounce away if not careful.— Dawn
- i used to think that condoms were rubber circles and i never knew how they stayed on— hello