Childlore is folklore passed directly between children, without the input of adults.
https://en.wikipedia.org/wiki/Childlore
Stuff I can think of off the top of my head are paper fortune tellers, summoning Bloody Mary/the candyman, the cool S, parody songs like “Jingle bells Batman Smells” and “Joy to the world, the teacher’s dead” etc.
This stuff has intrigued me since, well since I was a kid. I always wondered where they came from. I never saw adults doing that stuff, so I figured another kid had to have come up with it.
In my elementary school there was a rumour that kissing someone on the mouth makes a baby in the throat. I’ve heard it still being spread years later. There are also parodies of famous German poems that you have or had to memorize in school, although I some kids learnt them from their parents. I know parody versions of Die Glocke and Die Bürgschaft.
Soo… Does that mean you’re gonna give birth by coughing or vomiting up the baby?
I don’t think the kids thought that far. I certainly didn’t.