Old Chinese story from the Soushen ji (捜神記, "Record of investigations into the uncanny", i.e. "The X-Files"):

During the Qin dynasty, the Drophead people (落頭民, Luotou min) lived in the south. Their heads could fly. There was a festival among their tribes known as Bugdrop (虫落, Chongluo), and that's how they got that name.

Okay, wait. This tribe of people, this tribe whose heads can leave their bodies, they get the name "Dropheads" because of some bug festival? Really? This has to be a joke or reference that I don't get.

Wu General Zhu Huan (朱桓) once hired a certain servant girl. Every night after she went to bed, her head would part from her body and fly away. Sometimes it would get in and out of the building via the pet door, sometimes through a high window, but always using its ears as wings. It would arrive back just before dawn.

After a few nights of this, the servants who slept near her grew suspicious. One night they brought a lamp into the room and saw only a body, with no head. The body was slightly cold and its breathing faint.

The other servants covered it with a blanket and waited. As dawn approached the head came back, but with the blanket in the way it could not come to rest. It hit the ground a few times, groaning and grinding its teeth and looking most unhappy. Her breathing grew ragged and she looked very close to death. So they pulled away the blanket, whereupon the head leapt up again and reattached itself to the neck. Then all was calm again.

General Zhu found all this quite uncanny. It unnerved him so much that he fired her, and let her leave unmolested. It wasn't until later, when he investigated the matter further, that he learned that it had just been her essential nature.

That must have been an awkward conversation on many levels. "Yeah, I had to let this one girl go, she... well, her head came off and flew around." "Oh, you mean a Drophead? They all do that." "They all...?" "It's their culture, man. You aren't...?" "I... uh, no, no... I have tons of Drophead friends... it's just, I mean, the way it flew was against company policy, I couldn't..." "... Right, right... Listen, I have to get going..."

Other generals who went far to the south often captured Dropheads. One covered the neck of a Drophead with a bronze plate, preventing the head from rejoining the body and thus killing it.

Christ, what an asshole.

Presumably this is related to the Japanese rokuro-kubi (remember, Hearn's RKs' heads were fully detachable!), or derived from the same weird pan-Asian ur-source...