Zhou, a geographical division unit in China in the pre-Qin period, began to be used as an administrative division after the Eastern Han Dynasty. In the era of Three Emperors and Five Emperors (2607-2 BC110), there was Kyushu, that is, the world was divided into nine "states" at that time.
The word "Zhou" comes from "Chuan" and "Sa", and "Chuan" refers to the water flowing to the Sea of osawa, such as the Yellow River, the Yangtze River and the Huaihe River. The word "three" has the same sound and meaning as "main", meaning "moving in" and "moving in". Together, "Chuan" and "Sa" mean "living by the river" (building walls along the river to fight floods) and "living in water" (building walls on flat land and depressions to fight floods).