A bluecap is a mythical fairy or ghost in English folklore that inhabits mines and appears as a small blue flame. If miners treat them with respect, the bluecaps lead them to rich deposits of minerals.^[1] Like knockers or kobolds, bluecaps can also forewarn miners of cave-ins. They are mostly associated with the Anglo-Scottish borders.^[2]

Bluecaps were regarded as hard workers and it was said that they were expected to be paid a working man's wages, equal to those of an average putter (a mine worker who pushes the wagons). This payment was left in a solitary corner of the mine, and they would not accept any more or less than they were owed. The miners would sometimes talk of having seen a flickering bluecap settle on a full tub of coal, transporting it as though "impelled by the sturdiest sinews".^[3]

Another being of the same type (though less helpful in nature) was called "Cutty Soames"^[4] or Old Cutty Soames,^[5] who was known to cut the rope-traces or soams by which the assistant putter was yoked to the tub.^[4]