The Battle of Partholon's Sons
Trinity College Dublin MS H.3.17.
[This annecdote is extracted from the Senchus Mor. --MJ]
Ocus da mac Parthaloin is iat do righne in comrac, .i. Fer ocus Fergnia, ocus is uime ro comraicset, .i. in dara brathar dib, .i. Fergnia tuc a siar i Uanamnus, .i. lain, ocus tuc in brathair eile, .i. Fer, in tsuir eile, .i. Ain; ocus ro bi a cet coibchi, ocus ro ba leisim do reir dlighidh in coibchi, uair nir mair a athair; ocus a deir i Racholl m-breth [a]. "Leth cet coibci cacha mna da aigi fine, mad iar necaib a hathar;" ocus ro bai fergnia ac iarra a cothach don coibchi; ocus eisindraic he, ocus ni dlig ni; no is coibhche na sethar tuchadh aigidh i naigidh na coibchi so, ut dixit:--
"Da mac Partholain, cen acht,
Is iat rigni in comurc;
Fer is Fergnia, co meit nghal,
Anmanda in da brathar."
Ocus deismirecht ar in cetna:--
"Fer ocus Fergnia na fir,
Isedh innisit na sin,
Ain ocus Iain do certas sloig
Da prim ingin Parthaloin."
Is impusin srethaset in re ciata imairget; ocus a deir i mbaile [eile] Aine ocus Aiffe anmanda na da ingin.
Translation:
And it was the two sons of Parthalon that fought the battle, i.e. Fer and Fergnia, and the reason for which they fought was this: the one brother, i.e. Fergnia, married his sister, i.e. Ian, and the other brother, Fer, married the other sister, i.e. Ain; and the marriage gift which she received was her first marriage gift, and half the marriage gift belonged to him, according to law, because her father was not alive; for it is said in the Racholl Bretha "half the first marriage gift of every woman belongs to the head of her tribe, if she receives it after the death of her father;" and Fergnia was seeking his share of the marriage gift; but he was a disqualified person, and was entitled to nothing; or it was the marriage gift of the other sister that was brought face to face against this marriage gift, as the poet has said:-
"The two sons of Parthalon, without doubt,
"Were they who made the battle;
"Fer and Fergnia, of great valour,
"Were the names of the two brothers."
And this is an instance to the same effect :-
"Fer and Fergnia were the men,
"As the ancients do relate,
"Ain and Iain, who caused the hosts to be destroyed,
"Were the two chief daughters of Parthalon."
It was about these that the first battle-field ever fought was assembled; but it is stated in another place that Aine and Aiffe were the names of the two daughters.
SOURCE
O'Donovan, John, and Eugene O'Curry. Introduction to Senchus Mor and Athgabail. Ancient Laws of Ireland. vol. 1. Dublin: Alexander Thom: 1865. p. 154-155.