What do you mean by "ninth-rate people"

The so-called "people of the ninth stream" refers to people in the ninth stream.

And the "nine streams": Confucianism, Taoism, Yin and Yang, Legalists, famous artists, Mohists, military strategists, miscellaneous scholars and farmers. According to the traditional method, Jiuxi can be divided into Shangjiuxi, Zhongjiuxi and Xiajiuxi. Shangjiuliu: First-class Buddha, Second-rate Heaven, Third-rate Emperor, Fourth-rate Official, Fifth-rate Pavilion, Sixth-rate Prime Minister, Seven-rate (Jinshi), Eight-rate (Juren) and Nine-rate. Zhong Jiuliu: First-rate scholar, second-rate doctor, third-rate painter, fourth-rate skin (shadow play), fifth-rate actor, sixth-rate gold (divination), seven monks, eight roads and nine chess. The next nine streams: first-class platform, second-rate blowing, third-rate circus, fourth-rate pushing, fifth-rate pool, sixth back, seventh repair, eighth match and ninth prostitute.