What does Manchuria mean?

There are many theories about the origin of "Manchuria". One argument is that "Manchuria" is the homonym of the ancestors' names of Jurchen in Jianzhou. The second argument is that due to the rotation of five elements and five virtues in the ancient dynasty of China, the Ming Dynasty was a fire virtue, and the Chinese characters "Man" and "Zhou" were all beside the water character. This practice of Huang taiji is to put out the fire with water to make it clear. The third argument is that Manchuria is a transliteration of "Schumann", which is the name of Manjusri Bodhisattva by Tibetans, and its full name is Shuman Shili Bodhisattva. However, this statement is not recognized by most historians.