yeah it's mar as in car with an i as in e .
but if you want to get down and gaelic, if you are talking to mairie you say it var as in car with an i as in e, but if she's telling you her name it's as previously said. one of the wonderfull mind bogglers of gaelic is the case system where every thing has two or three pronounciations.
in irish the var becomes war as in car i think but i don't speak irish, i just read it a little. none of this digression affects the sining of the folk song i'm just being a bit obtuse. i once had someone ask me whether the boatman, fhir a bhata was pronounced as hear a vata or fear a bata, to which i had to say it depends on who you are talking to and what you are trying to say.
see why english people and gaels have trouble communicating , their languages don't even have the same concepts.