The Selgovae were a people of the late 2nd century who lived in what is now the Stewartry of Kirkcudbright and Dumfriesshire, on the southern coast of Scotland. They are mentioned briefly in Ptolemy's Geography, and there is no other historical record of them. Their cultural and ethnic affinity is commonly assumed to have been Brittonic.
Assertions that the Solway Firth preserves the name of the Selgovae are without foundation. 'Solway' is Anglo-Saxon from the thirteenth century (sol = 'mud', wæth = 'ford'), and this was the name of the main crossing at Eskmouth at that time. The firth has been known by various names in the past, and this one happened to be the survivor.
Read more about Selgovae: Contradicting Ptolemy