Is "Ordos" Mongolian? What do you mean?

Ordos is the name of a city in Inner Mongolia, which means "palace account" in Mongolian, and is often translated as "Ordor" in Mongolian classics. "Si" is plural: "many"

It is said that more than 700 years ago, the army of Genghis Khan, a generation of Tianjiao, passed by a plateau with abundant aquatic plants, bridled the reins for a long time, and said in poetic language that he chose a cemetery for himself after his death. After Genghis Khan's death, the all-powerful great man was buried here. Since then, this plateau has been named "Ordos", which means "palace account" in Chinese, because Genghis Khan's coffin was originally placed in eight White House accounts. There is also a name for the place where Genghis Khan is buried on the plateau, which means "master's graveyard".