Wu Zetian has no specific name. In 637 (the 11th year of Zhenguan), she was called into the palace as a talented person and was named "Mei Niang" by Emperor Taizong, hence the title of Wu Meiniang.
After her death, she was honored as "Emperor Zetiansheng" and "Empress Zetiansheng", so historians used to use your honorific title as her name and call her "Wu Zetian", which became the most popular title. In addition, she also invented the name "Zhao", which means "the sun and the moon are hanging in the air, shining on the earth", so it is also called "Zhao". But this name is not as widely used as the name Wu Zetian.