Kaluga, founded in the mid-14th century as a border fortress on the southwestern borders of the Grand Duchy of Moscow, first appears in the historical record in chronicles in the 14th century as "Koluga"; the name comes from Old Russian "kaluga" - "bog, quagmire". During the period of Tartar raids it was the western end of the Oka bank defense line. The Great stand on the Ugra River was fought just to the west. In the Middle Ages Kaluga was a minor settlement owned by the Princes Vorotynsky. The ancestral home of these princes lies southwest of the modern city.