Cousin Jack

A Cousin Jack could be a cousin named Jack- But back in the 1800s it could have been a miner of Cornish, English, Irish, or Welsh origin.  Another thing a cousin Jack could have been was a dugout that a miner lived in, roofed over with dirt providing insulation making it cooler in the summer and warmer in the winter.

A cousin Jack in Leadfield ghost town, Death Valley National Park