It was just probably just some poor guy with magical thinking OCD. "If I don't repeatedly draw symbols in the dirt, my whole family will die."

My head canon is that creatures such as ghosts, demons, djinns, ... enter our mortal realm willingly from time to time and sometimes form a connection with a person, who they then teach how to summon them in times of need. This knowledge is then passed down.

So effectively otherworldly creatures are tourists who gave a local their number and now they get bothered by their greatgreatgreatgreatgrandkids.

The Book of Enoch says that fallen angels named Uzza, Azza and Azael taught humans originally.

I like the idea that they're not just symbols, but shapes. Get anything to be shaped like a rune, and it'll touch magic. So two rocks leaned against each other just right might create a trickle of water, or a tree that grows a twisted enough web of branches could, by chance, summon a flame. Then, like with all natural phenomenon, people figured it out! It fits well with the trope that wizards are arcane researchers and scientists, you find in settings like D&D's