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.
Blowing in the Nintendo cartridge. Miss Mary Mack.
I have a child monitor that only charges if I blow in it before plugging it. It’s legit
I hear she dressed in black with silver buttons down her back.
The girl arts. Double dutch, the hand games like Miss Mary Mack and Bisquick, stuff girls seemed to spontaneously do that boys had nothing to do with. It feels like, when I was 6, the girls around me were always teaching each other stuff like that, and then by the time I was 16 it had transformed into teaching each other the cha cha slide. Done well those hand clap games and such could be impressive to watch.