Part 70 of The Metrical Dindshenchas

BRÉFNE

Whence derives the name of Brefne? seek it of scholars: for what cause was the name given to that land of abundant increase?
Whence derives the name of Sliab Fraech? ye seek of me the learned labour: tell me the famous cause whence Tuaim Regain is named.
Wherefore was the name Mag Slecht given to Mag Senaig of doughty deeds? tell on with toil and effort the legend of Mag Indusa.
Brefne, daughter of Beoan mac Bethaig, a brave soldier-woman, fell in conflict for that land with the Children of Ham, with their evil power.
Regan of the Children of impious Ham, from the army of strong-smiting Balar, was a warrior of prowess and exploits, whom none could face in equal battle.

Regan it was, dangerous beyond dispute, that engaged the combat; he was leader of the retinue of red-armed Oengus mac ind Oc, with all his army.
The warrior went his way in good sooth, when he had slain the soldier-woman, to demand an unjust tribute from the hosts of the Gael, though an unrighteous claim.
There met him, face to face, unaided, the king's son of the Gael; they fought a stern fight, hard by the rock of Asual's son.
The spot where the Fomoir's head was struck off—it was a doughty deed—is called after him Tuaim Regain: I hide not from thee the cause of the name.
Fraechnat of Cesair's following came to the mountain, witness of noble deeds: she rests under a bright windy grave-mound, and from her is named Sliab Fraech.
Indusa, daughter of long-lived Bress, of the Tuatha Dé Danann kind of face, perished by a deed of manly might at dreadful Mag Indusa.
Three thousand and ten hundred—this is the true complete account, a famous number—perished of their toil at the Plain of Prostrations.
Therefore was the name Mag Slecht given to Mag Senaig of doughty deeds, as verses reveal to the aged, since the time of Odbgen son of Sengann.

I am Fintan son of eager Lamech: I was a stark fighter in equal battle: I am versed in my time in the legend of Betha and of Brefne.