Meaning: an Irish masculine name of uncertain etymology, though it could possibly be related to Old Celtic bre meaning "hill" which, by extension, means "high, noble".
It could also be related to Celtic brig- or brigant- meaning "high"; briga- meaning "might" and "power"; or brigh- meaning "noble, strong, virtuous".
Brian Boru was a well-known Irish king in 10th century Ireland.
In Irish mythology, in the tale of The Fate of the Children of Tuireann, Brian, Iuchar, and Iucharba are three brothers who come across Cian, the father of Lugh, and whose families have been fighting for generations. Cian shapeshifts into a pig to get away from them but the brothers turn themselves into hounds and chase after him; they later kill him by pelting him with rocks.
When Cian's son Lugh goes looking for his father, he finds his body and discovers who the perpatrators are. In order to make them pay, he sends hem on a quest to retrieve seven magical objects all across the world which he plans on using in an upcoming battle with the Fomor. The brothers retrieve all the objects but on their last mission they are mortally wounded and plea for Lugh to allow them to use one of the items, a magic pigskin which heals all wounds. He refuses and the brothers die, and their father Tuireann dies of grief over them.