TommyKnockers

I saw the first episode of a new series on the SYFY channel, Ghost Mine, and it is basically about TommyKnockers.  The only association I had for that term was a Stephen King book about extraterrestrial aliens so I started the search!

That's an actual candle on the Cornish miner's helmet!

It turns out that TommyKnockers have nothing to do with aliens.  The term comes from Cornish folklore for a type of faerie, the equivalent of the Irish leprechaun.  TommyKnockers are small gnome-like creatures that inhabit mines.  As I have come to expect from these google searches, I came across a lot of contradictory information.  Sometimes TommyKnockers are considered helpful and friendly, leading miners to valuable ore and warning of cave-ins.  Other times they are vindictive, hurting or even killing miners.  I read that miners would not enter a mine unless they were assured that TommyKnockers had already started the job, or that miners would abandon mines as soon as TommyKnockers made their appearance.

Cornish miners emigrated to the U.S. and had a huge influence in the Pennsylvania coal mines and the California Gold Rush spreading the superstition of TommyKnockers.  But over the years TommyKnockers changed and instead of being Fae creatures, they became the ghosts of dead miners.
Apparently, with modern technology, TommyKnockers are supposed to be fading into legend.  But if this new show is any indication, people are just as superstitious as ever!