There are a few theories concerning the origin of the Old English Sheepdog (Bobtail).
One of them is that the breed comes from the Barbone and the Deerhound. Another one states that it comes from the Briard and the Bergamasco, and the third one says that the Old English Sheepdog is a descendant from a Russian dog called Owtchar, which was brought from the Baltic to the United Kingdom on ships.
The last theory is that the breed is a mix of breeds like the Bearded Collie and some other dogs brought from Russia, France, or the Baltics. The Old English Sheepdog was first developed in West England by farmers that needed herders for their sheep.