Cornish Knockers (or Tommyknockers) are mythical, dwarf-like mine spirits in Cornish folklore, tiny beings with large heads, long arms, and miner's clothes, known for mischievous pranks like stealing tools but also for warning miners of cave-ins with their distinctive knocking sounds, leading them to rich ore, or even being the ghosts of dead miners. Miners respected and appeased them with offerings (like parts of pasties) and avoided whistling, viewing them as protective guides or the spirits of fallen comrades, a tradition that travelled with Cornish miners to America, becoming a prominent part of mining lore.

Characteristics & Behaviour
- Appearance: Small, often described as 2 feet tall, with large heads, wrinkled skin, white whiskers, and dressed in miniature miner's garb.
- Activities: They knock on mine walls, which can signal rich ore veins or impending collapses. They hide tools, extinguish candles, and play tricks.
- Temperament: Generally mischievous but often helpful; they dislike whistling and seeing the sign of the cross.
- Offerings: Miners would leave the crusts of their Cornish pasties or other food as offerings for protection.
Origins & Beliefs
- Spirits of the Dead: Many believe they are the souls of miners who died in the mines, giving warnings to prevent others from the same fate.
- Fae Folk: Others see them as distinct fairy or goblin-like beings.
- Connection to Bucca: Related to the Bucca (or Bwcca), but separate entities, with both good (Bucca Gwidden) and malevolent (Bucca Dhu) aspects.
Legacy
- "Cousin Jacks": Cornish miners (known as "Cousin Jacks") carried Knockers lore to new mining areas, like Colorado, where they became known as "Tommyknockers".
- Pragmatic Roots: The legends likely arose as miners learned to recognize the creaking earth sounds as warnings, personifying them as spirits to cope with dangerous work.