Middle Mongol

Middle Mongol or Middle Mongolian was a Mongolic koiné language spoken in the Mongol Empire. Originating from Genghis Khan's home region of Northeastern Mongolia, it diversified into several Mongolic languages after the collapse of the empire. In comparison to Modern Mongolian, it is known to have had no long vowels, different vowel harmony and verbal systems and a slightly different case system.

From Wikipedia · Middle Mongol · CC BY-SA 4.0