The surname of ALLENSON was a baptismal name 'the son of Alwin'. The name has been common in England and Scotland since the 13th century. When the coast of England was invaded by William The Conqueror in the year 1066, the Normans brought with them a store of French personal names, which soon, more or less, entirely replaced the traditional more varied Old English personal names, at least among the upper and middle classes. A century of so later, given names of the principal saints of the Christian church began to be used. It is from these two types of given name that the majority of the English patronymic surnames are derived and used to this day. Most of the European surnames in countries such as England, Scotland and France were formed in the thirteenth and fourteenth centuries. The process had started somewhat earlier and had continued in some places into the 19th century, but the norm is that in the tenth and eleventh centuries people did not have surnames, whereas by the fifteenth century most of the population had acquired a second name. Early records of the name mention William Alisun, 1248 Berkshire. Henry Alleyson, was documented in the year 1332, in the County of Warwickshire. Patrick Alissone de Counte de Bercwyk, was one of the first to be recorded in Scotland in the year 1296. Peter Alesoun was a witness in Brechin in 1490. Gabriel Alason was baillie of the burgh of Dumfries in the year 1693. Ellesone Tayis was documented in Lanark in 1566. Between the 11th and 15th centuries it became customary for surnames to be assumed in Europe, but they were not commonplace in England or Scotland before the Norman Conquest of 1066. They are to be found in the Domesday Book of 1086. Those of gentler blood assumed surnames at this time, but it was not until the reign of Edward 11. (1327-1377) that it became common practice for all people.

The associated coat of arms is recorded in Sir Bernard Burkes General Armory. Ulster King of Arms in 1884.