I know all the tales of qarin, of jinn, of succubi, etc. Most are past human attempts to anthropomorphise a root cause for things like mental illness, seizures, etc. Some are parental attempts to scare children to stay near (such as the monsters, qualiput if I remember correctly, that live in the ice near Inuit villages). And yet others, if you look at modern medicine, are attempts to explain people such as dwarfs, primordial dwarfs, giants, etc., that we now know are simply humans with genetic and glandular issues. But in the past, would this child not have been thought to be a sprite?
Primordial Dwarfism creates a higher pitched voice, beak like nose, and a properly proportioned, though tiny child, who is more hyper and requires less sleep than other people. They are, as one mother described, like hummingbirds.
Take into account other things that can happen, the wide array of human maladie, deformities, accidents that can disfigure a person, and combine human ignorance, and you have a recipe for many monsters, goblins, and evil spirits that supposedly roam the earth.
