What is the origin of the saying "keep your dogs at bay?"

I believe the original phrase is 'keeping the hounds at bay' and refers to the way a hunted animal, such as a fox or rabbit, will run away from its young trying to led the dogs away from the nest, in other words, keeping the hounds on its scent. They generally bay, or bark, while doing this which signals to those left at the nest that they are relatively safe, the hounds are being 'kept at bay.'