Sheep-farmed?

 "He pointed out mountains that had been sheep-farmed by the first landholders." (from Photo Finish, by Dame Ngaio Marsh)

That is an interesting verb - "sheep-farmed." I had an English teacher friend once who observed that when we invent a verb, we generally do so in its regular form. For example, if we had trimmed our yard yesterday, most people would say that we "Weed-eated" or "Weed-eatered," instead of "Weed-ate."