The name Magheraboy doesn't receive a mention until 1585, when it is described in the
Composition Book of Connacht as "the halfe Toe (tuatha) of Magheraboy". It was the
Composition of Connacht in 1585, during the reign of
Elizabeth I, that most of the modern baronies and
counties of
Ulster would first be created. The barony's boundaries, however, coincide with those of an ancient territory known as
Tuath Ratha (people/tribe of the fort), the principal family of which was the O'Flanagans (), the ruling family of the
Cenél Cairbre Tuath Ratha. The O'Flanagans were an important medieval family based at Ballyflanagan (present day townland of
Aghamore) in Magheraboy, and they once controlled the entire western side of Lower Lough Erne from
Belleek to
Belmore Mountain. The O'Flanagans were related to the ruling family of the
Uí Néill kingdom of
Cairbre Droma Cliabh. Another small sept of the
Uí Néill, the
Cenél Láegaire, settled in Magheraboy in the early Christian period. ==List of main settlements==