What does "relief" mean and what allusion does it come from?

Pooping and peeing are called "relieving one's hands". This is the case in many places in our country. What is the relationship between defecation and defecation? It is said that it also comes from the migration of people under the ancient locust tree. It was only then that I opened my aunt.

Relocation is compulsory. People who are poor cannot leave their homeland and resist in various ways. Immigration officials and escorting policemen were afraid that they would escape halfway, so after the formation reached a full strength, they tied them up before setting off on the road. The first is heavy binding, that is, two arms are tied up, which makes it very inconvenient to move. Later, the "small tie" was used. Each person only tied one arm. Dozens of people were connected to a rope, and they were tied to each other. If one person moved, it would affect others, and no one could escape. Therefore, whether on the road or when resting at night, if someone among them needs to defecate or urinate. They were begging the escorting policemen to untie the ropes tied to their arms. In the beginning, in order to convey their meaning clearly, people said the words more completely: "Please, please untie my hands, I need to defecate (or I need to urinate)." Because there were many people, there were many times when people untied the ropes on the road, not only It's troublesome and wastes time. Because this method is safe and people can't escape, no matter how messy it is or how much time it wastes, no one dares to change it. Later, I talked more and gradually simplified the original words. First, he said: "Untie your hands for me", and you knew that he wanted to relieve himself; later, he simply simplified it to "untie your hands". As long as someone shouts "relieve", it means he needs to relieve himself. The sound of "relieving yourself" has been like this all the way every day, filling the eardrums. Everyone got used to it and used it.