In Celtic usage, Douglas means dwells by the dark stream. In England, Douglas means dark water. In the seventeenth century, this name was as popular for girls as for boys. In the Republic of Ireland, Douglas means flowing from the dark river. In Scotland, Douglas is from the Gaelic dubhglas meaning dark water, dark stream, or from the dark river. The Scottish Douglas clan had two historical branches: (Black Douglases and Red Douglases.) The lords of these clans figure in Sir Walter Scotts novels.