I cannot locate the origins of this figure of speech. Perhaps it was first used in a comedy sketch many decades ago, but it has since become a catchall for any criticism of a person who busily pursues low priority activities during a crisis. We imagine the eater chowing down on a five-course gourmet meal inside a besieged bunker or settlement as the bullets fly and the bombs fall. In a comical context, we laugh because the meal being eaten with such gusto seems so out of synch with the grave situation at hand. Beneath that laughter, as we all know, is our anxiety that we are witnessing a very unfunny distortion of priorities in dire circumstances.