Mortimer () is an English surname, and a given name (see Mortimer (given name)). Norman origins. The surname Mortimer has a Norman origin, deriving from the village of Mortemer, Seine-Maritime, Normandy. A Norman castle existed at Mortemer from an early point; one 11th century figure associated with the castle was Roger, lord of Mortemer, who fought in the Battle of Mortemer in 1054. The 12th century abbey of Mortemer at Lisors near Lyons-la-Forêt is assumed to share the same etymological origin, and was granted to the Cistercian order by Henry II in the 1180s.
https://en.wikipedia.org/wiki/Mortimer