Word Study
caponiere
CIDE DICTIONARY
caponiere, n. [F. caponnière, fr. Sp. caponera, orig., a cage for fattening capons, hence, a place of refuge; cf. It. capponiera. See Capon.].
A work made across or in the ditch, to protect it from the enemy, or to serve as a covered passageway. [1913 Webster]
For further exploring for "caponiere" in Webster Dictionary Online