During Spring and Autumn period, a monarch called Xiong Lv in the State of Chu in today's central China's Hubei Province was awarded with the title of King Zhuang of the Chu posthumously, and from then on, his descendants began to surname themselves Zhuang.
In Eastern Han Dynasty, Emperor Ming had a given name Zhuang. So he ordered the ordinary Zhuang-surnamed people to change their surnames to Yan in order to avoid the taboo of his personal name. This move contributes another part of surname Zhuang.
Some people with surname Yan shifted back to surname Zhuang during Northern and Southern Dynasties. Thus Yan and Zhuang came from the same family tree.
According to historical records, Yan people originated from Tianshui in today's Gansu province, Fengyi and Huayin in Shannxi province, northwest China. Later they moved southward, bringing surname Yan to the south.
By People's Daily Online