locket
    n 1: a small ornamental case; usually contains a picture or a
         lock of hair and is worn on a necklace

Locket \Lock"et\, n. [F. loquet latch, dim. of OF. loc latch,
   lock; of German origin. See Lock a fastening.]
   [1913 Webster]
   1. A small lock; a catch or spring to fasten a necklace or
      other ornament.
      [1913 Webster]

   2. A little case for holding a miniature picture or lock of
      hair, usually suspended from a necklace or watch chain.
      [1913 Webster]