Samhain was the New Year of the ancient Celts. The Celtic day started at sundown so celebrations were started in the evening. After the Christianization of the British Isles the Catholic Church failed to stamp out the people celebrating what was then considered a pagan event. Their solution "if you can't lick em join em" so they created the Christian holiday All Saints Day, but the people still celebrated Samhain as per custom on the previous evening so the church called it All Hallows Eve trying to make it reflect a Christian origin. It didn't fool the Celts though and many such as myself still celebrate it's arrival. Any song will suffice as long it's sung in the Gaelic tongue.