Wikipedia
Jagoldai
Jagoldai ( Tatar Turkic: ' Cağolday', Cağalday, , ) (pronounce: yah-gohl-DAI or jah-ghahl-DAY) – little Tatar Turkic tyumen (duchy) in today Kursk Oblast and Belgorod Oblast of Russia as well as the Sloboda Ukraine, vassal of the Grand Duchy of Lithuania in 15th-16th century.
It was founded in 1438 by Tatars of Golden Horde.