I can find no actual evidence of this but I have always interpreted pocky corses as corpses with the pox – that is, bodies that died with the plague or some other wasting disease that rots you before you get into the ground and probably even before you die. Or, like, leprosy, which might lose you whole portions of your body before you gave up the ghost. And all of that makes me wonder if the gravedigger is referencing a plague outbreak, and particularly, the one that closed London’s theatres for a bit. I imagine Shakespeare’s audience had recently seen more pocky corpses than they would have liked. So, too, they might particularly identify with a gravedigger who is irreverent with bodies. Probably the whole population had to get immune to dead bodies at a certain point – and a pocky corse might get you a laugh of recognition.