The surname Wu dates back to the offspring of Taibo and Zhongyong, both are sons of Gonggong Danfu (Old Duke Danfu) in Zhou Dynasty.
According to historical records, Taibo and his brother originally had the right to throne. However, they found that their father was especially fond of Ji Chang (i.e. later Zhou Wen Wang or Civil King), who was the son of their father's third son Ji Li, so they gave up their rights to Ji Li and then escaped to the area of Dong Wu (East Wu).
Taibo and Zhongyong called themselves "Gou Wu" and "Gong Wu" in Dong Wu area. Local people admired their moral integrity very much and followed their leadership. As the followers increased, they established the State of Wu and set Wu (today's Suzhou of east China's Jiangsu Province) as the capital.
Till the 19th grandson Shoumeng, the powerful State of Wu started hegemony. In late Spring and Autumn period, Fu Chai, king of the State of Wu, was taken in by the scheme of the State of Yue through enticing women and the State of Wu fell. In that disaster, large numbers of people of Wu were expelled out of their homes, some of whom fled afar and some fell slaves for the State of Yue.
The farther the Wu people were away from hometown, the more they missed it, therefore "Wu" more and more stood out as a symbol of blood tie and geographic relations. Having lost their country, people of Wu took "Wu" as their family name. Later, when the State of Yue perished, Wu people in Yue fled and many of them moved to the south, the farthest to Yangshan of Guangdong.
By People's Daily Online