The origin of the name is thought to be Norman,
One version is that it derives from "Mortemer", site of the Cistercian Abbaye de Mortemer at Lisors near Lyons-la-Forêt and close to Rouen in Normandy. The land was granted to the Cistercians by Henry II in the 1180s. Finding the land to be a marsh land area of the Lyons Forest around the running Fouillebroc Stream, the monks dug out a large drainage lake and built the Abbaye de Mortemer. The ruins and lake can still be visited, and the later 16th century Abbey hosts tours.
There are two possible explanations: first, a small pond must have already existed before the land was given to the monks and have already called Mortemer like the two other Mortemer, because the word mer 'pond' was not used anymore beyond the Xth century. This word is only attested in North-Western France and of Frankish or Saxon origin mari / meri 'mere', 'lake' (in Cambremer, Blingemer, etc..); mort(e) 'dead' is also quite common to mean 'stagnant' (in Port-Mort 'the port with stagnant water', Morteau 'dead water', etc.). Second, the monks could have given the name Mortemer to their drainage lake to remember the other Mortemer for any kind of reason we don't know, making a pun at the same time with Mer Morte 'Dead Sea'.
The village of Mortemer further north in the Seine-Maritime area bears the same name and it predates the Abbey at Lisors by more than one hundred years.
Another version, which appears at least as far back the Elizabethan Era, attributes the name to a Norman knight who fought in the crusades and was distinguished in battle by the shores of the Dead Sea, (Mer Morte in French,) but this is unsubstantiated and almost certainly a romanticised myth.
In the Middle Ages, the Mortimers were a powerful magnate family or dynasty of Marcher Lords in the Welsh Marches, centered on Wigmore Castle in Herefordshire, and from the 14th century holding the title of Earl of March.
Through marriage, the Mortimers came during the reign of Richard II to be close to the English throne, but when Richard II was deposed in 1399, the claims of the Mortimers were ignored and the throne vested in the usurper Henry of Lancaster instead. The Mortimer claims were later (1425) transmitted to the House of York, which ultimately claimed them in the Wars of the Roses.
Members of the noble Mortimer family included:
Ranulph de Mortimer, Lord of Wigmore Castle in Herefordshire and Seigneur of St. Victor-en-Caux, today Saint-Victor-l'Abbaye, Seine-Maritime, Upper NormandyHugh de Mortimer, Lord of Wigmore CastleRoger Mortimer of WigmoreRalph de MortimerRoger Mortimer, 1st Baron Mortimer (1231–1282)Isabella Mortimer, Countess of Arundel (after 1247–before 1 April 1292/after 1300)Edmund Mortimer, 2nd Baron Mortimer (1251–1304)Roger Mortimer, 1st Earl of March (1287-1330)Edmund Mortimer (1302–1331)Katherine Mortimer, Countess of Warwick (1314–1369)Agnes Mortimer, Countess of Pembroke (1317–1368)Roger Mortimer, 2nd Earl of March (1328-1360)Edmund Mortimer, 3rd Earl of March (1352-1381)Edmund Mortimer (1376-1409), fought with Owain Glyndŵr and plotted with Henry Hotspur Percy to depose King Henry IV of EnglandRoger Mortimer, 4th Earl of March (1374-1398)Edmund Mortimer, 5th Earl of March (1391-1425)Bob Mortimer (born 1959), English comedian and actorCarole Mortimer (born 1960), English romance novelistChris Mortimer (born 1958), retired Australian Rugby League playerConor Mortimer, Irish Gaelic football playerDaniel Mortimer (born 1989), Australian Rugby League playerEdmund Mortimer (actor) (1874–1944), American actor and film directorEmily Mortimer (born 1971), English actressFavell Lee Mortimer (1802-1878), English Evangelical author of educational books for childrenGary Mortimer (born 1967), English aeronautGeorge Ferris Whidborne Mortimer (1805–1871), English schoolmaster and divineHarvey Walklate Mortimer Senior (1753-1819) and Junior (1776-1850), English gunmakers on Fleet Street in London.Ian Mortimer (born 1983), Canadian sprint canoerIan Mortimer (historian) (born 1967), British writerJames Mortimer (1833–1911), American chess player, journalist and playwrightJames Mortimer (athlete) (born 1983), New Zealand hurdlerJohn Mortimer (1923-2009), British barrister, dramatist, screenwriter and authorJohn B. Mortimer, Hong Kong judgeJohn Hamilton Mortimer (1740–1779), British painterJohn Robert Mortimer (1825–1911), Yorkshire corn merchant and archaeologistKenneth Mortimer (president), President Emeritus of Western Washington University, eleventh president of the University of Hawai`i system and Chancellor of the University of Hawai`i at Manoa from 1993-2001Minnie Mortimer (born 1980), fashion designer and socialitePeter Mortimer (disambiguation)Roger Mortimer (racing) (1909–1991), racing correspondentSteve Mortimer (born 1956), former Australian Rugby League playerTinsley Mortimer (born 1976), American socialiteTony Mortimer (born 1970), British songwriter, composer, singer and rapper; member of British 1990s pop group East 17Colonel Douglas Mortimer, played by Lee Van Cleef in the film For a Few Dollars MoreDr. Mortimer, a character in the Sherlock Holmes novel The Hound of the Baskervilles by Sir Arthur Conan DoylePhilip Mortimer, a protagonist in Blake and Mortimer, a Belgian comics series created by Edgar P. JacobsMortimer Brewster, a protagonist in Arsenic and Old Lace and its film adaptationMortimer Goth, a character in the life simulation games The Sims, The Sims 2 and The Sims 3Mortimer Harren, a male crewman in Star Trek: Voyager", appearing in the episode 'Good Shepherd'Mortimer Mouse, a Disney character and rival of Mickey MouseMortimer Scharff, the driver of the hearse Shadow in the popular destruction derby franchise Twisted Metal.Mortimer Delvile, a character in the novel Cecilia by Frances BurneyMortimer McMire, the primary antagonist of the Commander Keen seriesMortimer Toynbee (Toad), a mutant in the X-Men comicsMortimer "Morty" Smith, one of the two lead characters in Rick and MortyMortimer "Morte" Rictusgrin, a character and companion in the video game Planescape: Torment