The Collaborative International Dictionary of English v.0.48:

Fob \Fob\ (f[o^]b), n. [Cf. Prov. G. fuppe pocket.]
   1. A little pocket for a watch; -- callled also a watch
      pocket.
      [1913 Webster]

   2. a short chain or ribbon attached to a pocket watch,
      usually worn hanging out of the watch pocket, and used to
      conveniently remove the watch from the watch pocket.
      [PJC]

   Fob chain, a short watch chain worn with a watch carried in
      the fob; a fob[2].
      [1913 Webster]

WordNet (r) 3.0 (2006):

watch pocket
    n 1: a vest pocket to hold a pocket watch [syn: fob, watch
         pocket]