My great grandmother was Catherine McKerrell, daughter of James McKerrale (also spelt mckerale, mckerrall, mccairal and lots more)and Sarah Tru (or Threw). There is a castle in the Scots borders country belonging to the McKerralls which is supposed to have an association with William Wallace ? Macairel was an heir to the Kings of Ulster and there are many McKerrells to this day on the Mull of Kintyre, especially at Southend and Campbelltown, as well as some in northern Ireland.
If you are interested I can send you more information (which I have at home) if you'd like to reply. I am at work and have stumbled on this forum quite by accident.