Daqin (literally “Great Qin”) was the historic name for the Roman Empire in China. This name comes from the Chinese dynasty founded by Qin Shihuangdi, which ruled the Qin state. This ruler was also the first emperor of a united China in 221 BCE.
The state of Qin encompassed the northwestern lands of present-day China and marked the beginning of the silk road (in the east). Whereas the Roman Empire was at the west end.
The name Daqin was used on Chinese maps until the 16th century. After the fall of the Western Empire, it was used for a long time to describe Byzantium.