And bringing a dictionary of Irish terms.....
'Mearing drain'
"Mearing" most commonly refers to a boundary or a line marking a limit. It can also be a surname, or a term for a boundary between pieces of land, particularly in Ulster (Northern Ireland).
Despite having a Limavady Grandma I cannot recall her saying this word despite that she lived on one side of what would be a mearing drain here in NZ.
I love this site for all the terms and the by the by snippets.

I do remember my mother being most emphatic that her McIntyre close friend was descended from Ireland and came from Ireland to NZ. Way back they may have come from Scotland.....