the battle of the boyne was between catholics and protestants, which the catholics out numbered the protestants 4-1, a couple of tactical blunders resulted in protestants winning, the song derives from there, the catholics where there to kill protestants as well, but for celtic not to respect one minute for men who gave there all was sickening, they are anti british, don't really see them selves as scottish, so they cling to this ****ing idea the irish they are the gypsy kurds of europe