The word "Yi San" derived from the mongol word which is derived from the chinese word "Yi Shang" （衣裳）， meaning clothes, lit. "the coat and the skirt". The robe itself presents a wonderful mixture of mongol and chinese clothing and was very popular among military men of the Ming Dynasty, including the emperors.
Patterns available including "Fei Yu" (lit. flying fish, like dragon but with a fish-like tail), and "Dou Niu" (lit. fighting bull, like dragon but with its horn like a bull). Both are mystical dragon-like creatures. Historically, since the dragon patterns were strictly reserved for the royalties, Ye Sa robes of these patterns were issued by the emperor to his officers who had extra outstanding achievements.