Here is a story: it is said that when Jigong was alive, there was a very greedy and powerful official, and now there is a housekeeper under him who is very overbearing. On one occasion, an official asked the poor to pay for the bridge, put a big box in it and asked people to put money in it. Jigong cast a spell, and the official put his foot in it, and one leg became a copper coin. So he asked Jigong to treat him. Jigong said that the only way was to change his leg. The official said that the housekeeper is usually the most loyal. If he wants to change his leg, the housekeeper has no choice but to do so. So the official's leg was cured, but the housekeeper had no leg, so Jigong changed the housekeeper's right hind leg, which is the origin of the "dog leg". But the dog has no legs, so Jigong made a leg out of mud and gave it to the dog. Because it is made of mud, you should pick up the dog every time you pee to avoid getting wet. Of course, this is an allusion. In fact, when a male dog lifts his leg to pee, the first thing is to leave his own smell on the ground, and the second thing is instinct and habit. But not all male dogs do.