Source : Webster's Revised Unabridged Dictionary (1913)

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

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

Source : WordNet®

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