Why does the word "underworld" use the word "Cao"?

Cao doesn't mean surname here, and it has nothing to do with Cao Cao. It refers to Gong Cao. Gong Cao was originally a feudal official name, also known as the history of Gong Cao, which was established in the Western Han Dynasty. He used to be the chief assistant of the magistrate and county magistrate, and was in charge of the election department. The six merits in the myths and legends of the underworld in China are the official names of the underworld: Qin, who specializes in the records of life and death, birth and death; Unified management of ghosts' punishment and good or bad luck in the afterlife. He has "Six Gong Cao" under his command, and there are three in the left class, who are in charge of Cao Tian, Cao Di and Cao Ming respectively; Three students in the right class are in charge of God Cao and Ghost Cao respectively. Cao Liu's duty is to present the official documents and newspapers of the underworld to Yin in time, and quickly spread the imperial edicts of Yin to all places. According to folklore, whenever the world needs to ascend to heaven, it will be "presented" after being burned by Gong Cao, and then the official documents and reports will be presented to Yan Luowang by the Gong Cao God next to Yan Luowang.