How does Xuanwu explain it?

Xuanwu is a spiritual thing composed of turtles and snakes. Xuanwu originally meant Xuanming, and the ancient sounds of Wu and Ming are interlinked. Xuan means black; Ghost means yin. At first, Xuan Ming described the tortoise's divination as follows: the tortoise's back is black, and the tortoise's divination is to invite the tortoise to the underworld to ask questions, bring back the answers and show them to the world in the form of divination. Therefore, the earliest Xuanwu is the tortoise.