The land where Tianjin is located today was created in prehistoric times by sedimentation of various rivers entering the sea at Bohai Gulf, including the Yellow River, which entered the sea in this area at one point.
As for the origin of the name of "Tianjin", there are diverse viewpoints in history. The Origin from Literature: Tianjin as a word initially appeared in poems of Qu Yuan, a famous patriotic poet of Chu State in Warring States Period. In his masterpiece named Li Sao( The Outlet of Sorrow and Dissatisfaction), there is a verse(At dawn, departing from the Port of the Heaven).
The Origin from Astronomy: Tianjin also used to be a name of the star official in Chinese traditional astronomical system. It was recorded in Astronomy Record in Book of Sui. The Origin from a River Named Tianjin-It was recorded in River Record in History of Jin. The Origin from Emperor’s Name-giving-This perhaps is the most reliable point of view. Tianjin means literally The Ferry Site of Emperor (The Son of Heaven). It was said that Emperor Chengzu, who was one of sons of Emperor Taizu of Ming Dynasty, before his enthronement, for getting the crown of Emperor, launched a war against the successor of Emperor Taizu, Zhu Yunwen, the grandson of Emperor Taizhu, in Nanjing. He departed from Gu River of Tianjin. After his success in enthronement, he presented his departure site a name – Tianjin.
The opening of the Grand Canal of China during the Sui Dynasty prompted the development of Tianjin into a trading center. Until 1404, Tianjin was called "Zhigu", or "Straight Port". In that year, the Yongle Emperor renamed the city Tianjin, meaning "the Heavenly Ford", to indicate that the Emperor (Son of Heaven) forded the river at that point. This is because he had indeed forded the river in Tianjin when in contention for the throne with his nephew. Later, a fort was established in Tianjin, known as "Tianjin Wei", the Fort of Tianjin
