These days, parents quite often just choose a name for their child because they like the sound of it and think it goes with their surname. This is quite new, however, as naming patterns used to dictate at least the first child's name and the same few choices popped up generation after generation.
First sons were often named after their fathers, second sons after their mother's fathers and third sons were frequently named for their father's father. This pattern would be repeated by each subsequent generation. Sometimes, though, the expected boys did not arrive and a poor little baby girl just got her Dad's name with an 'a' or 'ina' chucked onto the end. This works well for Alexandra, Davina and Georgina, but we have also found Keithinas, Hughinas and an Edwardina.
At least these poor girls' parents at least made an effort to feminise their names. It seems that a lot of no-nonsense Orcadians could not be bothered with this skittering about and just gave their daughters the male names. Christian was not often softened to Christina and there are a lot of women called Christian to be found in the birth, marriage and death registers. Stuart was also thought to be an appropriate name for a woman and appears surprisingly often. We have also found photographs of a few Graham's with long hair and frilly skirts.
It was also not unheard of to give children a surname as a first name so, just as you find Mackenzies and Campbell's today, there are quite a few Baikies and Crawfords to be found in our censuses. Again, most of them are female.
My fave Orcadian surname as a forname so far is the delightful Honeyman which I have only come across in men so far. Honeyman Flett, Honeyman Moar, Honeyman Manson etc...