Sir Furry, this is of special interest to me because long ago I worked with a woman, last name Severn! Now you show us it is the name of a river in Wales -- Wales has EVERYTHING! Wikipedia even has a map of its watershed, it's the biggest/longest/everythingest river around...special affection for one of its tributaries, the Vyrnwy...how Welsh can a river get?
Another tributary over by Wolverhampton, close to one of my Quora friends, in the Black Country of England, so named after the Industrial Revolution got started there, and left its black ash...Wikipedia wants me to credit the author of this map, so here he is: By ChrisJB (talk) - Own work, CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=4392685