Muscovy
This was the region of Asia that eventually became Russia. It was named for the Moskva river, which borders the area to the west. From that grew the city of Moscow, which became the center of Grand Duchy of Muscovy.
It was first mentioned in the 1200, and they fought off the Mongols in the 1300s.
Why I Looked It Up
In Shogun (set in 1600), the main character is describing the areas of the world they have mapped:
His hand eliminated everything in North America noth of a line from Mexico to Newfoundland, everything in South America, apart from Peru and a narrow strip of coast land around that continent, then everything north and east of Norway, everything east of Muscovy, all Asia, all inland Africa, everything south of Java and the tip of South America. “We know the coastlines, but little else. The interiors of Africa, the Americas, and Asia are almost entirely mysteries.”