They say that the pig was Wotan's sacred animal. He was a Norse god who paralleled jesus quite a bit - virgin birth - dad was god - was sacrificed by being nailed to a tree and so on. Wednesday is Wotan (WodensTaeg) Day - and Wotan was nailed to his tree at Easter (like jesus), and this is why the traditional Easter meal is ham.
Some places in England, so I've heard, Wotan is still worshiped.