The Lord God had created all animals, and had chosen out the wolf to be his dog, but he had forgotten the goat. Then the Devil made ready and began to create also, and created goats with fine long tails. Now when they went to pasture, they generally remained caught in the hedges by their tails, then the Devil had to go there and disentangle them, with a great deal of trouble. This enraged him at last, and he went and bit off the tail of every goat, as may be seen to this day by the stump. Then he let them go to pasture alone, but it came to pass that the Lord God perceived how at one time they gnawed away at a fruitful tree, at another injured the noble vines, or destroyed other tender plants. This distressed him, so that in his goodness and mercy he summoned his wolves, who soon tore in pieces the goats that went there. When the devil observed this, he went before the Lord and said, "Thy creatures have destroyed mine." The Lord answered, "Why didst thou create things to do harm?" The Devil said, "I was compelled to do it: inasmuch as my thoughts run on evil, what I create can have no other nature, and thou must pay me heavy damages." - "I will pay thee as soon as the oak leaves fall; come then, thy money will then be ready counted out." When the oak-leaves had fallen, the Devil came and demanded what was due to him. But the Lord said, "In the church of Constantinople stands a tall oak-tree which still has all its leaves." With raging and curses, the Devil departed, and went to seek the oak, wandered in the wilderness for six months before he found it, and when he returned, all the oaks had in the meantime covered themselves again with green leaves. Then he had to forfeit his indemnity, and in his rage he put out the eyes of all the remaining goats, and put his own in instead.
This is why all goats have devil's eyes, and their tails bitten off, and why he likes to assume their shape.