Strathclyde (lit. "Strath of the River Clyde"), originally or Alclud, was one of the early medieval kingdoms of the Britons in the Hen Ogledd, 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.