Cheng Miao was a courtling in Qin dynasty. He was thrown into Yun Yang county ( Today's north-western of Chun Hua in Shanxi province) prison because of a fault. With nothing to do in prison, he was then thinking to change the way to write Xiao Zhuan, which is the popular and official script in Qin dynasty. After ten years of work in prison, he created 3000 Li Shu characters. He gave those characters to Qin Shi Huang (the first emperor of Qin). Qin Shi Huang was pleased and highly appreciated the characters. He then instated him as the Yu Shi (a high post).
At the time, the memorials to the throne was getting more and more. Zhuan Shu is hard and complicated to write. So Qin Shi Huang decided to use Li Shu. Since it's facilitate the works of low post officials, it is called Li Shu. Li means low post officials.