What's the name of Duke Zhou in Butterfly of Duke Zhou?

Duke of Zhou is an ancient book about dream interpretation and divination. It is said that it was written by Duke Zhou, and its dream interpretation was derived from Zhouyi. Duke Zhou, whose real name is Ji Dan, the son of Zhou Wenwang, is the author of Zhouyi. He helped become a king and consolidated the rule of the Zhou Dynasty. Being revered as a saint by later generations is an idol worshipped by Confucius. Confucius once said, "I haven't dreamed of Duke Zhou for a long time." Express admiration for Duke Zhou. Therefore, dreaming is called "seeing the Duke of Zhou"