Much like the name origination for Caerlaverock, the name for the River Nith was derived from a descendant of Coel Hen Godhebog, a prince of Cumbria. Nuath was a son of Coel Hen Godhebog and owned lands in Annandale and Clydesdale which were named after him - Caer-nuath of Carnwath. The River Nith owes its name to this son of Coel Hen Godhebog - Nuath.
One of Nuath's descendants, Loth, a Pictish king, is responsible for the Lothian name. Marken, a brother of Loth, had a son named Kinder, who had a son named Yrvin. This Yrvin owned lands in Eskdale named after him, and from which the Irving family is named.