The Collaborative International Dictionary of English v.0.48:

Piggin \Pig"gin\, n. [Scot.; cf. Gael. pigean, dim. of pigeadh,
   pige, an earthen jar, pitcher, or pot, Ir. pigin, pighead, W.
   piccyn.]
   A small wooden pail or tub with an upright stave for a
   handle, -- often used as a dipper.
   [1913 Webster]