Dumb me. I should have looked further in my own notes before posting.

According to the Mormon IGI, Ellinor Waterson McDonald was the daughter of Robert Waterson and Elinor Quark. Ellinor was christened in August 1713 and married John McDonald on 26 November, 1727 -- at the age of 14! A very young bride, indeed.

I'd like to know more about these Watersons.