The Collaborative International Dictionary of English v.0.48:

Shillalah \Shil*la"lah\, Shillelah \Shil*le"lah\, n.
   An oaken sapling or cudgel; any cudgel; -- so called from
   Shillelagh, a place in Ireland of that name famous for its
   oaks. [Irish] [Written also shillaly, and shillely.]
   [1913 Webster]

WordNet (r) 3.0 (2006):

shillalah
    n 1: a cudgel made of hardwood (usually oak or blackthorn) [syn:
         shillelagh, shillalah]