Tommyknocker

Knockers are small supernatural beings associated with mines. They may interfere with tools or food, but their sounds can also warn miners of an approaching collapse or draw attention to valuable ore.

Cornish mining traditions traveled with emigrant miners and became part of North American mining folklore, where “tommyknocker” became a familiar name. Some accounts describe little mining figures; others connect the beings with spirits of the dead.

• Wikipedia contributors, “Knocker (folklore)”; secondary reference overview.