The Collaborative International Dictionary of English v.0.48:

Pigskin \Pig"skin`\ (p[i^]g"sk[i^]n`), n.
   1. The skin of a pig, -- used chiefly for making saddles;
      hence, a colloquial or slang term for a saddle.
      [1913 Webster]

   2. A football; -- so called because the covering is often
      made of pigskin. [Colloq.]
      [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

pigskin
    n 1: leather from the skin of swine