Hubby's granddaddy, Brice Larimer McClure, wrote this note about his ancestry some 70 years ago. The note says that Robert Larimer--born in the north of Ireland--married Mary O'Gallagher or Gahaler in American about 1741 or 1742. Robert and Mary are hubby's 5th g-grandparents. He's the Larimer who was shipwrecked (I've written about it here).
From the well-researched book "Our Larimer Family" by J.C. Work and A. Work (available as a digital download here), I know Mary and her husband Robert lived in the Kishacoquillas Valley of Pennsylvania. This valley was settled from the 1720s on by Scotch-Irish folks.
A search for the valley AND the name "O'Gallagher" turns up essentially nothing, but searching for the valley AND "Gallagher" turns up a number of entries. These may be clues that Mary's name was actually Gallagher, from a Scotch-Irish family.