When I was little, I played a video game called "The Legend of Zelda" in which the hero must rescue the kidnapped Princess Zelda. From that I divined that this new word "legend" meant that someone was kidnapped and you had to save them; I thought that a game called "The Legend of Your Pets" would be pretty fun.
(Eventually in school they taught me that a "legend" was something found on a map. This didn't help.)
A childhood belief about speaking

others believed things like this
- I used to believe that the game The Legend of Zelda: Twilight Princess was the longest game ever.Anon
- I used to believe the spleen was an urban legend— Nikki
- I believed the urban legend that gum stayed in your stomach for 7 years if you swallowed it.— Lindsay
- When I was a child I used to believe that when I played video games my real world changed like the game. — J
- I used to believe that the brown UPS trucks kidnapped kids.— Kim
- My mom used to think "preschool" was called "pretty school" until a few years later.— Molly