For more on the Scottish tune Gilderoy, which spread throughout England and Ireland and was used by Cathal McGarvey for his new song, Star of the County Down around 1920 or so, see, amongst others, this thread:  Songs to Star of the County Down

Apparantly, the song My Love Nell, which John Hill referred to above, was written by William Carleton (in the 1860s?), to the same traditional air, which he knew as "Come All Ye".  Carleton was a stage entertainer in America who apparantly specialised in Irish subjects, often comic; not to be confused, I assume, with the popular Irish novelist of the same name who lived around the same period.  There is a songsheet at the Library of Congress  America Singing   collection:

My Love Nell

Malcolm