1A mysterious light supposed to be seen floating or flickering in the air around a corpse, in a graveyard, etc.; a phosphorescent light emitted by decaying organic matter; (also) a luminous electrical discharge on a ship, etc., during a storm, St. Elmo's fire. Compare death candle death-flame , death light .
2A fire for burning a person to death.
Mid 18th century. From death + fire.