Strathclyde (lit. "Strath of the River Clyde", Welsh: Ystrad Clud and Strað-Clota in Old English), was a Brittonic successor state of the Roman Empire and one of the early medieval kingdoms of the Britons, located in the region the Welsh tribes referred to as Yr Hen Ogledd (“the Old North"), which comprised the Brythonic-speaking parts of what is now southern Scotland and northern England. The kingdom developed during Britain's post-Roman period. It is also known as Alt Clut, a Brittonic term for Dumbarton Castle, the medieval capital of the region. It may have had its origins with the Damnonii people of Ptolemy's Geography.