Medieval European miners believed in underground spirits. The kobold filled this role in German folklore and is similar to other creatures of the type, such as the English bluecap, Cornish knocker and the Welsh coblynau. Stories of subterranean kobolds were common in Germany by the 16th century. Superstitious miners believed the creatures to be expert miners and metalworkers who could be heard constantly drilling, hammering, and shoveling. Some stories claim that the kobolds live "in" the rock, just as human beings live in the air.