ハイズオン
The name first appeared officially in 1498. In feudal times, Hải Dương indicated a vast area from east of Hanoi to the sea. This area corresponds to all of modern Hải Dương, Haiphong, most of Hưng Yên and the southwestern corner of Quảng Ninh. Hải Dương city is in the middle of this historical area and was the location of a citadel defending the capital. Because of this historical location, "Thành Đông" (eastern citadel) is a common nickname of Hải Dương. The name "Hải Dương" (海陽) comes from Sino-Vietnamese and means "ocean sun" in English.