Originally the loinclothes of Giants, the cape is a cloth device that prehistoric man drapped across his shoulders in attempt to hide himself from the giants. Unfourtunately, the Giants would simply find the loin clothes laying around and put them back on. The only problem was that the people were stil hiding beneath them, leading to a enorumous number of humans being shoved up the asses of giants.
The Anusians believe that mankind as we know it started in a Giant's anus, and right now we are all festering in the dung and cracks of the large instestine, but that is totally irrelevent to the definition of a cape. In modern times they are known to be worn by superheroes to obtain a more aerodynaic frame for flying, and by small children seeking to augment their ESP powers.