The Normans arrived with surnames that had already been well established in England, France, and what's now northern Belgium. Also, the Barons that came north with David I from England kept the names they had—Balliol, Bisset, Bruce, Comyn, Fraser, and Montgomery—when they settled on lands in Scotland.
At that time, Scotland had two cultures, the Highland Gaelic and the Lowland Anglo-Saxon. In the Highlands, life was more primitive, so surnames weren't as much a part of life as they were in the Lowlands. Those who belonged to a clan were the exception.
Highland chiefs demanded absolute loyalty from members of their clans, so each male member took the chief's surname, using "Mac," the Gaelic word for son, resulting in names such as MacDonald and Maclaren. Some Mac surnames originated in occupations, such as Macnab (son of the abbott), Maccosh (son of the footman), and Macmaster (son of the master or cleric). Many Mac surnames, such as Macolchallum, are no longer used because they were too difficult to pronounce. Mac surnames can also be spelled using "Mc."
Many beginning genealogists believe that those who bear a clan surname are automatically descended from a clan chief. This isn't necessarily so. The ability of a clan to defend its territory from other clans depended greatly on having a large number of people in it. Being a member of a large and powerful clan gave less powerful men an advantage in the lawless Highlands, so followers might adopt the clan name to gain favor with the chief, to show solidarity, for basic protection, or because a more powerful neighbor had taken their lands. However, not all members of a clan used the clan surname. When Clan Gregor was denounced in 1603, many Macgregors adopted surnames such as Campbell, Grant, Ramsay, or Stewart to avoid persecution.
When it became necessary to distinguish ordinary people from one another by more than just their given name, the use of Scottish surnames spread. However, in some areas of the Highlands, fixed surnames didn't become common until the 18th century.
External influences also played a major role in the shaping of Scottish surnames. The migration of the Scots from Ireland into the Southwest in the 5th century, the influence of the resident Picts, the establishment of the Britons, and Anglian immigrants along the Borders, all contributed to today's Scottish surnames.
The Vikings also influenced surnames in Scotland. The word bairn refers to a child in the dialect of the Scottish Lowlands. A pretty child might be given the name Fairbairn-in English, Fairchild. The Norsemen left the marks of their culture all along the western shores of Scotland. The name Gunn, originally derived from the Norse, is common in the North of Scotland while the Old Norse name Thorburn is seen in the Scottish borders.
Many Scottish surnames originated in patronymics. Unlike using a prefix to indicate a familial relationship, in patronymics a son's surname comes from his father's forename. For instance, Donald Johnson's son might be Paul Donaldson, whose son might be Magnus Paulson. This presents a challenge for beginning genealogists since the surname changes with each successive generation. This practice persisted in the Highlands well into the 18th century. In earlier records, a person might be known not only by the father's name but also by the grandfather's name.
Some Scottish surnames come from offices or titles held by the person. That includes everyone who held serving positions or titles within the royal or noble household. A title that started humbly but became the family name of royalty was the House of Stewart: Walter FitzAlan was the Steward (someone who ran the household) for the Kingdom of the Scots under Robert Bruce. The word "steward" originated from an Old English term meaning "sty ward" or keeper of the animals, but later changed to mean the supplier of the master's table. Domestic staff became known for their official duties. For instance, a general servant was known as a Hine or Hind while the Chamberlain worked within the noble's private chambers.
While "Mac" preceded most of the Highland surnames, the name, itself, often indicated the person's occupation rather than his name. For instance, MacIntyre is the son of the Carpenter or Wright and MacIntosh is the son of the Chief.
To further distinguish between persons of the same name, people started to add descriptive names that indicated the person's height, skin and hair color, strength, or frailty, or a physical feature or an attribute. Names based on hair color include Reid for red, Brown, White and Black. Small or Little refer to height definitions. The name Cruickshanks indicated crooked shanks or legs. Armstrong showed the strength of an individual.