This isn't me, but a friend of mine when she was little heard her mom call her female anatomy her vagina, well she thought it was called a "from China" as an inside joke we now call it our "from China's"
A childhood belief about rude bits

others believed things like this
- When I was a little girl, I thought all babies came from 'China' (a Vagina)— Lainie
- When I was younger I was certain my "private" was called a ba-china... the boy's were pickles. — taliba
- Until about 2nd grade, I thought they spoke Spanish in China.Anon
- Me and my sister used to dig holes in the yard because we thought we could dig to china.— Savannah
- When i was little for some reason i thought that all people from china knew karate.....yeah.— sneakydean
- I used to believe that went the sun went down, it went down into the ground over in China.— Danielle, AL