I originally thought "balls" was slang for buttocks instead of testicles.
A childhood belief about rude bits

others believed things like this
- I used to think that girls had "balls" and not boys, and the "balls" were slang for breastsAnon
- Since my father had a deep cleft in his chin, I thought he was growing a tiny buttocks out of his face.— Rick
- i always thought it was Grape Balls of Fire instead of Great Balls of Fire— Courtney
- For whatever reason, I thought that grass was slang for tobacco rather than marijuana.Anon
- I thought “Orgy” was slang for orgasm until I looked up the definitionAnon
- I used to think that poop was stored in your buttocks and that's why they're squishy.Anon