They were lineal descendants of the "hard tack" that was a core part of the food supplied onboard ship from at least the sixteenth or seventeenth centuries. Hard tack wasn't really biscuit in the modern sense of the word; it was a form of fat-free bread that had been cooked twice to remove all traces of moisture. This meant that, kept dry, it would keep indefinitely without spoiling.

As such, hard tack wasn't designed to be eaten like a biscuit, either; it had to be moistened to be palatable. Normally it would be dunked into whatever stew was being cooked up on board ship, or in the trenches.