Because 'Sandy' is William's mother's name?? Remember, names like Alexandrina (which was Queen Victoria's first name) were quite common up there (although generally a bit later than this), and a name like Alexandrina, or Alexandra (the female version of the very popular man's name in Scotland - Alexander), would be quickly shortened to 'Rena', 'Sandra', and perhaps even 'Sandy'. Sandy, Sanny, and Sawney are the common diminutives of Alexander, but I can see no reason why a woman might not also have the soubriquet 'Sandy'. Also, as you point out, spellings could be very hit-and-miss, and the general populace was mostly illiterate at this time. Just an idea. Lachie