I've never heard of it (and I'm Irish born and bred), unless it's a mis-spelling of Gallagher (pronounced Gal-ih-her)?
It comes from the country of Ireland. It is an Irish last name.
ireland
Ireland
Ireland
Ireland
This last name is from Ireland and Spanish
It comes from the country of Ireland. It is an Irish last name.
ireland
Ireland
Ireland
Ireland
Ireland
Ireland
Ireland
Ireland
Ireland
Presumably Ireland or Scotland.