When someone is 'elevated to the peerage', the title chosen is at the discretion of the monarch and is determined by factors such as geographic connections and historical precedent.
Lord Redesdale, the father of the Mitford sisters, was the 2nd Baron Redesdale and had a connection to Northumberland's Redesdale valley. The Mitford family, with origins in Northumberland, owned land in the area, including Mitford Castle near Morpeth. The family was elevated to the peerage twice, in 1802 and 1902, with the title Baron Redesdale being recreated in 1902. Lord Redesdale's father, David Freeman-Mitford, was the 2nd Baron Redesdale, linking the family to the Redesdale valley.
