The term "Ghost Light" began in the Theatre industry.
What is the point of a ghost light?
The practical use of a ghost light is mainly for safety. A ghost light enables one to navigate the theater to find the lighting control console and to avoid accidents such as falling into the orchestra pit and stepping on or tripping over set pieces.
Some say it is meant to chase away mischievous spirits; or to light the way for the ghosts to keep them happy and contented.
Sara Bareilles' song is so worth a listen...
Peace to you my fellow souls