It started in the Song Dynasty.
In 111 BC (the sixth year of Yuan Ding in the Western Han Dynasty), Liu Che, Emperor Wu of the Han Dynasty, was very happy after the army of the Han Dynasty pacified Lingnan (now a small part of Guangdong, Guangxi and Hunan). In order to consolidate the existing achievements and reassure the people, Liu Che, the Emperor of the Han Dynasty, issued an edict saying, "When Guangdong is first opened, it is advisable to spread kindness and trust", which means that local officials should use the favor of the imperial court to govern Lingnan area and let the local people live and work in peace.
Later, in order to please the emperor, officials in Lingnan named the county as Guangxin County (the original location of Guangxin County was Wuzhou City, and the other was Fengkai County in Guangdong Province).
in the song dynasty, for the convenience of management, the court took guangxin county as the boundary, east of guangxin county was called guangnan east road, and west of guangxin county was called guangnan west road. Guangdong and Guangxi are derived from the abbreviations of "Guangnan East Road" and "Guangnan West Road".
Historical facts before Guangdong and Guangxi:
Guangdong and Guangxi were one family for a long time in history. At that time, they were collectively called "Lingnan". Of course, Lingnan not only included Guangdong and Guangxi, but also some areas of other provinces.
In the Tang Dynasty, Lingnan Road was set up, which governed Guangdong, Guangxi, Yunnan and Jiaojiao. In Xian Tong, Tang Yizong for three years, it should be divided into Lingnan West Road and Lingnan East Road for the sake of convenient management. The West Road is located in Tanzhou and the East Road is located in Guangzhou.
above content reference: Baidu Encyclopedia-Guangdong and Guangxi