Peasants here traditionally kill their pigs on 22 december, because of some saint day or the winter solstice . After the pork is killed, usually by having his throat cut but the EU is changing that, it is covered with hey that is set alight. These is done to burn the hair and cook somewhat the pig skin that becomes an appreciated dish called ?orici (foreigners don't seem to like this salty specialty, dunno why) There are many stories about pigs that were not really dead and who were woke up by the burning hey and who chased people around and set fire to haystacks or barns. It is possible that these stories are amplified by the large quantities of alcohol that accompany this occasion but I can imagine a drunk roman peasant watching the scene of chaos that a resurrected burning pig created and deciding that it could be a useful weapon against those weird Lucan oxen that are afraid of mice.
I've heard that Americans like to cover pigs in oil and then try to catch them but it may be just an exaggerated tale about those exotic, distant lands. The origins of this noble sport may come from roman soldiers who tried to recover a pig that was already covered with pitch for the purpose of being used against elephants.