I wonder how the middle finger display came to be called "the bird". In the thirties there was a raucous noise called a "Bronx cheer" made with the mouth, but sounding like loud flatus,which was also called a "razzoo" or a bird.I think it died out because of the retort, "now do one with your mouth!" Another bit of repartee from that period was to call someone a ziegus, alleging that they blew their nose on toilet paper, because their face looked so much like their ass, their bowels did not know which way to run. It was a period of obvious taste and refinement.