Autumn trousers, as the name implies, are trousers worn in autumn. In fact, they are comfortable and close-fitting pants that are worn under the outer pants to keep warm when the temperature is cold. Generally, when the weather turns cold in autumn, wearing a pair of trousers is not enough to keep warm, so adding a pair of close-fitting trousers to the trousers is called autumn trousers, which is a northern vocabulary. In the south of Huaihe River, it is called cotton trousers, and in some places it is also called underpants. Autumn trousers belong to underwear and can't be worn outside.