This surname is derived from a geographical locality. 'de Mortimer,' Latinized in old rolls into de Mortuo Mari, i.e. Dead Sea. Lower says it was for this reason that the surname was supposed to have sprung from Crusading times. 'The castle and barony of Mortemer lie in the arrondissement of Neufchatel in Normandy': Patronymica Britannica.

Ralph de Mortimer, Lincolnshire, 1273. Hundred Rolls.

Hugh de Mortuomari, Herefordshire, ibid.

Lucia de Mortuomari, Herefordshire, ibid.

Sir Robert de Mortimer, Norfolk, 1381: History of Norfolk.

Willelmus Mortimere, 1379: Poll Tax of Yorkshire.

1581. William Mortimer, Wiltshire: Register of the University of Oxford.

1601. James Mortimer, Cardiganshire: ibid.

This surname is derived from the barony of Mortemer (Latinized Mortuum Mare) in the arrondissement of Neufchatelen-Bray, Normandy, which name again is a modified form of the name given to the North Sea (Oceanus septentrionalis) by the Cimbri. Pliny in his Historia Natumlis (IV, c. 27) mentions that Philemon (a geographer of whom nothing is known), who may have derived his knowledge from traders, says the Cimbri call the North Sea Morimarusa, that is the "dead sea," as far as the promontory of Rubeas (Philemon Morimarusam a Cimbris vocari, hoc est mortuum mare, usque ad promontorium Rubeas), The name is Celtic. The first part is mori, a neuter i-stem (Stokes, Urkeltischer Sprachschatz, p. 217), Old Irish muir, found also in the latter part of the name of the Aremorici ("those who live by the sea"), the old name of the inhabitants of Brittany. The second part of the name is - marvo-s, "dead," (ibid., p. 203), Irish and Gaelic marbh.

The first of the name recorded in Scotland is probably William de Mortimer who sometime after 1165 witnessed King William the Lion's confirmation of the charter of Philip de Euermel to Neubotel (Neubotle, 126), and as William de Mortuo Mari witnessed Radulf de Clere's gift of the church of Caledoure to the Abbey of Kelso, c. 1170 (Kelso, 348). He was taken prisoner in 1174 at Alnwick along with the king (Bain, II, p. 117), but apparently soon afterwards released as he appears as witness in a charter of King William to the Abbey of Arbroath, c. 1178-82 (RAA., II, 535), and c. 1200 he witnessed the gift of the churches of Camsi (Campsie) and Altermunin to the Abbey of Kelso (Kelso, 226). About the year 1210 Roger de Mortuo Mari witnessed the confirmation charter by William the Lion of the church of Trauement (Tranent) to the monks of Holyrood (LSC., 38), and between 1200 and 1214 he witnessed a confirmation by the same king in favor of Arnbroath (RAA., I, 93 bis). About 1225 this Roger also witnessed the confirmation by Alexander II of his father's grant of right of a fair, etc., to the bishop of Glasgow (REG,, p. 113). Walter de Mortuo Mari is mentioned c. 1200 as "tunc decanus ecclesie Glasguensis" (Kelso, 148), Hugo de Mortuo mari, prior of May, before 1214 (Melros, 53) witnessed a gift of five acres of land called "elwaldescaleslonigge" in the territory of Stainthon to the Abbey of Melrose, John Mortymar was burgess of Dundee in 1406 (REB., II, 12), and George Mortimuir was retoured heir of Captain John Mortimuir of Glencat, Aberdeenshire, in 1695 (Retours, Aberdeen, 496). The Mortimers disappeared as landlords in Aberdeenshire in the first half of the seventeenth century, and the last in direct line of Mortimer of Auchinbady, an old Banffshire family, died in 1716 leaving two heiresses.

"Mortimer's Deep" is the name given to the passage between the mainland and St. Cohn's Inch in the Firth of Forth. The legend told to account for the name relates that Alan Mortimer, lord of Aberdour, bequeathed a tract of land near Aberdour to the monks on condition of his body being buried within the hallowed precincts of Inchcolm. "The monks carrying his corps," says Sibbald, "in a coffin of lead, by barge, in the night time, to be interred within their church, some wicked monks did throw the samen in a great deep, betwixt the land and the monastery, which to this day by the neighbouring fishing-men and salters is called Mortimers Deep" (History of the sheriffdoms of Fife and Kinross, 1803, p. 92). Mertimer 1702, Mortymer 1471.Stolen from Fore-bears

This name was latinized de Mortuo Mari, and hence the notion that the name was borrowed in crusading times from the Dead Sea in Palestine. The castle and barony of Mortemer lie in the arrondissement of Neufchatel in Normandy, and of course remote from the sea; but it appears that the expression mortua mara was sometimes applied to stagnant waters by the Normans, and at Mortemer there was a small lake so designated. The patriarch of this family in England was Ralph de Mortemer, who came in at the Conquest, and held immense possessions in many counties, the head of his barony being Wigmore Castle, co. Hereford.

The name is of Norman origin. The Scottish branch of the family are descended from Alanus de Mortimer, who in 1126, acquired the barony of Aberdour by marriage with the daughter and heiress of John de Vipont.