Middle names became more popular towards the end of the 19th century. It was not unusual to step outwith the traditional Sc naming pattern, middle names were often the name of the laird or an employer, keeping in with the boss. Maybe this is a NE Scotland custom - my father named my brother and me after grandparents, but 3rd child has middle name of his rich great aunt (it worked!) and 4th child includes forename of a colleague who was always good to his family.
I understand that at the first baptism by a new minister, the minister's names were added to the child's.
BTW, a mother would often stick in the surname of the father as a middle name if child illegitimate.
I have a great grandfather George Thom b 1840, cannot find him in OPRs, but illegitimate and been given surname of birth father (as his mother did for the other 3 illegitimate children she had, all by different men). Married 1867, 2nd son born 1869 was George Scott Troup Thom, informant was father plain GT. Most later births plain GT except one in 1876 when he is GSTT. 1871 census he is GT and son is George S T Thom Junior; this son dies 1880 and henceforth now consistently uses middle names.
Looks like he added middle names in later life when his job situation improved. (His mother was Scott, but see no familial connection to Troup.) Or used it more to in rememberance of the son who died. Or like first post, it is a plain name - there might be another person similarly named, possible in same area or type of job, and they needed to differentiate.
Have yet to look up Kirk Session records for my naughty GG grandmother!
Hope this helps
