What is "tsurube-otoshi"

Tsurube-otoshi (釣瓶おとし) is a creature from Japanese folklore. It lurks in the tops of trees and drops down on unsuspecting humans, and has various descriptions - sometimes it is some sort of oni or tengu, sometimes it is a disembodied head, and sometimes it is a fireball. Its name is an expression for "falling quickly" which literally means "a well-bucket dropping", and sometimes the tsurube-otoshi instead drops a well-bucket to scoop up its prey.