 The title is a reference to "The Communist Manifesto" which in  English begins: "A spectre is stalking Europe, the spectre of  Communism." The French translation known to Buñuel translated  "spectre" as "fantome". So the title can be seen as a dig at the  "Bourgeois" mentality which fears freedom, and also a sideswipe at  the rather straightjacketed Communist parties of the time.