Wikipedia
Tianzhu is the historical East Asian name for India. Originally pronounced xien-t'juk, it comes from the Chinese transliteration of the Persian Hindu, which is itself derived from the Sanskrit Sindhu, the native name of the Indus River. Persians travelling in northwest India named the region after the river around the 6th century BC. Tianzhu is just one of several Chinese transliterations of Sindhu. Shēndú ( OC n̥i[ŋ][d]ˤuk) appears in Sima Qian's Shiji and Tiandu is used in the Hou Hanshu (Book of the Later Han). Yintejia comes from the Kuchean Indaka, another transliteration of Hindu. A detailed account of Tianzhu is given in the "Xiyu Zhuan" (Record of the Western Regions) in the Hou Hanshu compiled by Fan Ye (398–445):
Tianzhu was also referred to as Wutianzhu (, literally "Five Indias"), because there were five geographical regions in India known to the Chinese: Central, Eastern, Western, Northern, and Southern India.
In Japan, Tianzhu was pronounced as Tenjiku. It is used in such works as the Japanese translation of Journey to the West.
In Korea, Tianzhu was pronounced as Cheonchuk. It is used in Wang ocheonchukguk jeon, meaning An account of travel to the five Indian kingdom, a travelogue by the 8th century Buddhist monk Hyecho from the Korean Kingdom of Silla.
Tianzhu (Chinese: 天主, Tiānzhǔ), meaning "Heavenly Master" or "Lord of Heaven," was the Chinese word used by the Jesuit China missions to designate God.