Why is Cao Sijie called Cao Sijie?

Sorry, I don't know the specific information of "Cao Sijie Gou". The following is additional information based on your question:

Caosijiegou is a place name in Sichuan Province, which is named after local legends.

Legend has it that in the middle of19th century, a local woman named Cao married a foreign woman named Dai. Shortly after marriage, Dave went out to sell salt and didn't come back for many years. His wife is anxious to ask around. After learning that her husband was doing business in Chaozhou, Guangdong Province (now Guangdong Province), she went to find it alone. But there are so many people, I can't understand dialects, but I can't find a husband. Finally, I stayed in Chaozhou, helpless, but fortunately I was taken in by a charity and raised in an orphanage. Later, the local squire set up a workshop for his affairs to show "chastity". The masses felt that he was miserable, and they donated money and materials to help him tide over the difficulties. Later, Cao Shi was instructed to return to his hometown. Because Cao Shi ranked fourth, it was named "Caosijiegou".

I hope the above information is helpful to you.