Tianzhu is where today Tianzhu means

India. In Chinese history, the earliest record of Tianzhu is in the "Historical Records of Dawan Biography", which was called body poison (Indus Sanskrit sindhu antiphon) at that time.

Book of the Later Han Dynasty and the Western Regions.

Biography records that "a person in Tianzhu Country is poisonous". At the beginning of the Tang Dynasty, it was collectively called Tianzhu. Four empires have appeared in the history of Tianzhu: the Peacock Empire.

The Gupta Empire, the Delhi Sultanate, and the Mughal Empire.

Since the Western Han Dynasty, the body poison, Tianzhu, and faith are all Sanskrit.

The transliteration of sindhu refers to the radiation area of the Indus Valley, not the entire South Asian continent.

Tang monk Xuanzang.

He went to the Western Regions to learn from the scriptures, and was the first to name "India" according to the pronunciation of indu, "the name of Fu Tianzhu, the dissent dispute, the old name is Shen Du, Shen Poison, Xian Dou, Tianzhu, etc." Today from the sound, Yiyun India".

Tianzhu was the name of the Tang Dynasty, including today's India, Pakistan, Bangladesh, Nepal and other countries.

India, Pakistan, Bangladesh and other countries. Hope it helps.