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.
On another kid’s hand: “Circle, circle, dot, dot. Now you have your cooties shot.”
That is not sufficient cootie protection. A properly trained physician will follow it up with
Circle circle, square square,
Now you have it everywhere
No cootie insurance though