How do you know that Dou E is from the south?

Dou E was a four-person in the south of Yuan Dynasty. Dou E was a native of the Yuan Dynasty, which practiced the policy of national oppression and divided the whole country into four classes. The first class is Mongolian, the second class is Semu, the third class is Han, the fourth class is Nanren, that is, the people of all ethnic groups in the Southern Song Dynasty, and Dou E is Nanren.