Eldest son - named after his paternal grandfather
Second son - after his maternal grandfather
Third son - after his father
Fourth son - after his father's eldest brother

Eldest daughter - after her maternal grandmother
Second daughter - after her paternal grandmother
Third daughter - after her mother
Fourth daughter - after her mother's eldest sister

The order is sometimes reversed i.e. the eldest son is named after his maternal grandfather, and eldest daughter is named Younger children would be named after earlier forebears, but the pattern in their case was less settled."
Source: "In search of Scottish Ancestry" by Gerald Hamilton-Edwards, Phillimore, 1983 Edition

In Scotland - as in the rest of Western Europe - there were four main ways of acquiring a surname:-

Patronymic - taking the father's Christian name e.g. Robertson
Occupation - e.g. Smith (the most common surname of all)
Locality - e.g. Wood
Nickname - e.g. White, Little.

Patronymics - Lowland names such as Wilson, Robertson, Thomson and Johnson are among the most common surnames in Scotland. 'Mac' names are also patronymic. MacManus - son of Magnus. 'Mc' is just a printer's contraction and has no significance as to etymology.

Occupation - Names which are derived from trades and occupations - mostly found in towns. The most common of these is Smith (the most common surname in Scotland, England and the USA) but other examples would be Taylor (tailor) Baxter (baker) and Cooper (barrel maker).

Locality - In Scotland the tendency is for people to be named after places (in England the tendency is the opposite). Examples of such names are Morton, Lauder, Menzies and Galloway.

Nickname - Names which could refer to colour or size, e.g. White, Black, Small, Little. Scottish names in this category include Campbell (meaning 'crooked mouth'). Another example of nickname - this time referring to the bearers origins - is Scott.

For more detailed information try this web site.