What is "qasar"

Qasar (also spelled Hasar or Khasar, and also known as Jo'chi Qasar; Mongolian: Хасар) was one of Genghis Khan's three full brothers. According to the Jami' al-Tawarikh, his given name was Jo'chi and he got the nickname Khasar after his distinguished bravery. He was also called Habutu Hasar (Хавт Хасар, Hasar the Skillful (archer)) because he was skilled with a bow.