[15] Although the Loígis were originally from Ulster in the north, Lugaidh Laeighsech led his tribe into the southern conflict at the request of his foster father, Eochaid Find Fuath nAirt ('Eochaid the Fair, Art's Abhorrence').
For his own part in that campaign Eochaid similarly won for the Fothart tribe, which was named after him, territories in what are now Counties Kildare, Wicklow, and Carlow.
As compensation for expelling the Munster men from Leinster, the Loígis tribe received not only the territory that came to bear their name, but also certain hereditary rights that the king of Leinster bestowed on the tribe's chieftains, who were from that point recognized as kings of Loígis (ríg Laíchsi/ rí Laí[gh]si) in their own right.
[20] English etymologists since the eighteenth century have held that the word sept, which specifically applies to the Irish clan structure, is derived from the Latin septum, meaning literally 'a hedge or fence' and figuratively 'a division'.
[21] One nineteenth-century scholar of Irish history, however, suggested that sept might alternatively have derived from the Latin septem, 'seven', and argued that the number seven had particular relevance to peoples of Cruthin or Pictish origin, like the Loígis, who invariably divided their tribes into seven parts.
[23] Nevertheless, no text explicitly named the seven septs before 1607, when they were identified as the "Moores and their followers, the Kellies, Lalors, Clanmelaughlins, Clandebojes, Dorans, and Dolins".
[24] That appeared in a report to the Privy Council, where Arthur Chichester (1563-1625), the Lord Deputy of Ireland, said that chronic rebellions throughout the island had been inspired primarily by the seven septs of Queen's County.
[27] It was not until the 19th century that all of the seven Loígis septs were definitively identified with a fixed group of surnames, which were the "O'Mores, O'Kellys, O'Lalors, O'Devoys or O'Deevys, Macavoys, O'Dorans, and O'Dowlings".