A person who tends the fire for a steam engine
A person (originally a man) who keeps the fire going underneath a steam boiler (originally, shoveling coal by hand), particularly on a railroad locomotive or steamship.
A safety inspector in coal mines.
An assistant on any locomotive, whether steam-powered or not.
Someone (especially one who is male) who is skilled in the work of fighting fire.
A relief pitcher (reflecting the figurative analogy of rescuing the situation).