Yorkshire Fog that is, Holcus lanatus, although grasses are difficult to identify so I may have dropped a clanger here. No doubt someone will put me right. And it may well be a double clanger. A hog is a young sheep, one or two years old that hasn’t been sheared. Count as poetic licence.
Back to the Yorkshire Fog, the name is popularly thought to come from the misty effect when the large moorland swathes are seen from a distance, but more likely the name comes from the Old Norse word fogg meaning long damp grass.