Source : Webster's Revised Unabridged Dictionary (1913)

Codpiece \Cod"piece`\, n. [Cod, n., ? + piece.]
   A part of male dress in front of the breeches, formerly made
   very conspicuous. --Shak. Fosbroke.

Source : WordNet®

codpiece
     n : (15th-16th century) a flap for the crotch of men's
         tight-fitting breeches