How did the title of the Forbidden City come from?

This is closely related to the ancient astronomical geography of China and the feudal superstition of emperors. The "purple" in the Forbidden City means that the purple is unchanged. Astronomers in ancient China divided the stars in the sky into three constellations, 28 constellations and other constellations. The three Hang Seng Index are Taiwei Hang Seng Index, Ziwei Hang Seng Index and Shi Tian Hang Seng Index. Ziweiheng is in the middle of the three horizontal lines, so it is called the emperor. Because the Forbidden City is the highest-level "forbidden place" in the hierarchical feudal society, the word "forbidden" in the Forbidden City just emphasizes the incomparable dignity of the palace. In ancient times, people believed that the Jade Emperor lived in the Heavenly Palace, which was called the Purple Palace. The feudal emperor claimed to be the "son of heaven", and his residence was equivalent to the "Purple Palace" in the sky (also known as Wei Zi Palace). In feudal society, the palace where the emperor lived was surrounded by high and thick walls, so it was called the Forbidden City. At present, the Forbidden City, like the Great Wall, is one of the most important tourist attractions in China, and it has become an important part of the history and culture of China. As for when the title of the Forbidden City came into being, in the poem "Give Cherry" in the Kaiyuan period of the Tang Dynasty, You Wei once said: "Furong closes a thousand palaces, and purple is forbidden." It can be seen that the palace has been called "Purple Forbidden" in the Tang Dynasty.