zwieback

In ages past, keeping food fresh for any length of time required a lot of ingenuity, especially when one needed to carry comestibles on a long journey. One of the solutions people came up with for keeping bread edible for traveling was to bake it twice, thereby drying it and slowing the spoiling process. The etymology of zwieback reflects this baker's trick; it was borrowed from a German word that literally means "twice baked." Nowadays, zwieback is not just used as a foodstuff—the texture of the dried bread makes zwieback a suitable teething device for infants. Incidentally, other twice-baked goods whose origins reflect that fact include biscuit and biscotti, both of which come from phrases meaning "twice-cooked bread."