The Collaborative International Dictionary of English v.0.48:

Keepsake \Keep"sake`\, n.
   Anything kept, or given to be kept, for the sake of the
   giver; a token of friendship.
   [1913 Webster]

WordNet (r) 3.0 (2006):

keepsake
    n 1: something of sentimental value [syn: keepsake,
         souvenir, token, relic]