souterrain

plural souterrains

1. archaeologyAn underground chamber or passage sometimes used as a store, especially one associated with Iron Age settlements.

   Now when my son saw that I separated them, he secretly built this souterrain and furnished it and transported to it victuals, even as thou seest; and, when I had gone out a-sporting, came here with his sister and hid from me.

   1885, Sir Richard Burton, The Book of the Thousand Nights and a Night, Night 11