Strathclyde (lit. "Strath of the River Clyde"), originally Cumbric: Ystrad Clud or Alclud, was one of the early medieval kingdoms of the Britons in Hen Ogledd ("the Old North"), the Brittonic-speaking parts of what is now southern Scotland and northern England. The kingdom developed during the 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.