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.
I’ve heard of this (way after the fact). IIRC it was part of some player’s guide, and may have been included either as a joke by the author or a copyright trap by the publisher.
Seems I was right. Per this wiki article Apologies for linking to Fandom.
Wow, I never heard it was written down anywhere. I never bought unofficial guides, either, though I did subscribe (rather, my parents subscribed me to) Nintendo Power. Not sure if they wrote it in an article in a magazine, or if I just heard it on the playground.
Either way, that’s pretty common with maps. Map makers will invent towns that do not exist, and if they see other map makers using it, they know their work was stolen.