3-B:
The "custode" I found in my Shorter Oxford was actually a noun, meaning custodian or guardian. Either way, it's a valid word.
Incidentally, should the letters ever come up, you can play "custodes". It's in the list already, as the plural of "custos", a Latin-derived word, also meaning custodian, but more particularly it's a title given to certain officials in the Franciscan order.