What is the origin of the old name of the Forbidden City?

The emperor pretended to be the son of the emperor of heaven, that is, the son of heaven. Tiangong is the place where the Emperor of Heaven lives, and naturally it is the place where the Emperor of Heaven lives. "Guang Ya Shi Tian" says: "The name of the Heavenly Palace is Purple Palace." Therefore, the palace where the emperor lived was called the Purple Palace.

2. The origin of the Forbidden City is related to the ancient theory of "imperial wall".

Ancient astronomers divided the stars in the sky into three-walled and twenty-eight star constellations. Three walls refer to Qiu wall, Shi Tian wall and Wei Zixing wall. Wei Zixing Yuan, known as the Emperor, is located in the center of Sanyuan. Purple MSI is the Big Dipper, surrounded by stars. In ancient times, there was a saying that "purple is above the middle" and "Emperor Taiping sat in the middle, and Qing officials were divided into four seas". Since the ancients compared the son of heaven to Wei Zixing Yuan, Wei Zixing Yuan became the land of emperors, so the Forbidden City was called Ji Zi, Ziban and Ziyuan.

3. Legend of Purple Gas from the East:

This is related to the ancient allusion of "purple gas coming from the East". Legend has it that Laozi went through the customs to Hangu Pass, and the purple gas was seen by the guards from east to east. Not long after, Lao Tzu came riding a green cow, and the breeder knew that this was a saint. The gatekeeper asked Lao Tzu to write the famous Tao Te Ching. Therefore, purple gas is considered auspicious, indicating the emergence of sages and treasures. Du Fu's poem "Autumn Prosperity" said: "Look at the Yaochi in the west, the Queen Mother will descend, and the purple gas will fill Dongguan." From then on, the ancients called the auspicious Qi Ziyun, the legendary immortal's residence as Hai Zi, the immortal as Ziquan and the suburban road as Mozi. Purple gas comes from the east, symbolizing auspiciousness. It can be seen that the "purple" of the Forbidden City is well-known. The place where the emperor lived was so heavily guarded that ordinary people could not enter it, so it was called the Forbidden City.