So, I've been researching my genealogy and I have discovered something interesting and am a bit confused? I have been researching my line of male ancestors. I am doing this by their first name and last name as we have 6 generations I can find online with the same name. But, when I got to the 6th generation I hit a wall, but on one of the listings of the sons of my ancestor he has his mothers surname,(McRae) as his first name and his fathers last name as his regular surname. But, my first name is also a surname. So, I was wondering if this was a thing in scotland to name a son after the mothers surname.
Well, more like it became a thing starting in the 1500s for English-based cultures to use a surname as a given name, and a mother's maiden name was a likely source.
Scotland had two cultures (Highland and Lowland), and the Lowland culture was closely related to English culture. The Scots language is either a language closely related to English, or a dialect of English -- opinions differ. And the personal naming conventions were and are pretty similar, though with regional variations.
From the 1500s, English gentry started using surnames as given names. You may have heard of one example: Guildford Dudley, husband of Lady Jane Grey (who was de jure queen of England for 9 days between the death of Edward VI and Mary I showing up with an army). E. G. Withycombe, The Oxford Dictionary of English Christian Names, pp. xli-xlii, gives another early example: Warham St. Leger (b. 1525). She also adduces Essex in the 17th C, a daughter of Lord Paget, whose father was an earl of Essex, though she implies that it was less common for girls.
As it happened, for both Guildford and Warham, those were their mother's respective maiden names.
As for why? Camden wrote in 1605 that "it seemeth to proceed from hearty good will, and affection of the godfathers to shew their love, or from a desire to continue & propagate their own name to succeeding ages". He also gives examples of several heirs general (apparently meaning from a collateral branch) who had as given names the surnames of the original line. (Depending on the wording of a title or will, there could be inheritance through women.) He also states that it was done in other countries "by such as would be Godfathers, when they were more than half fathers" -- meaning for bastards.
She also states that it continued as a gentry custom until the 19th C, when it became more general. And she also lists some surnames that are now used as given names without anyone realizing it or having a connection: Percy, Sydney, Neville, Russell, Howard. I would add Madison to the list.