Scottish English German and Dutch: from the personal name Alexander classical Greek Alexandros which probably originally meant ‘repulser of men (i.e. of the enemy)’ from alexein ‘to repel’ + andros genitive of anēr ‘man’. Its popularity in the Middle Ages was due mainly to the Macedonian conqueror Alexander the Great (356–323 BC) - or rather to the hero of the mythical versions of his exploits that gained currency in the so-called Alexander Romances. The name was also borne by various early Christian saints including a patriarch of Alexandria (c. 250–326 AD) whose main achievement was condemning the Arian heresy. The Gaelic form of the personal name is Alasdair which has given rise to a number of Scottish and Irish patronymics for example McAllister . Alexander is a common personal name in Scotland often representing an Anglicized form of the Gaelic name. In North America the English form of the surname has absorbed cognates from other languages e.g. Spanish Alejandro Italian Alessandro Arabic or Assyrian/Chaldean Iskandar and Iskander and their derivatives e.g. Greek patronymic Alexandropoulos. Jewish: from the adopted personal name Alexander (see 1 above) or shortened from the eastern Ashkenazic (originally Slavic) patronymics Aleksandrovich or Alexandrowicz.
Source: Dictionary of American Family Names ©2013, Oxford University Press