subs. (racing).A saddle. Hence KNIGHT OF THE PIGSKIN = a jockey.
d. 1870. DICKENS [quoted in Century]. He was my governor, and no better master ever sat in PIG-SKIN.
1898. The Sporting Times, 26 Nov., 3, 3. After a few days rest he was in the saddle and has again electrified English turf followers by riding rings around their crack KNIGHTS OF THE PIGSKIN.