An ancient race in Munster, a portion of the O'Donovans became Cairbre Eva (or Uí Chairpre, see map) within the ancient regional kingdom of the Uí Fidgenti, once approximately co-extensive with the modern County Limerick, and were for many centuries allies of the Eóganachta, to whom they were related by common descent from Ailill Flann Bec (or Ailill Aulom). Although allowed to be princely "in multiple ancient sources", in the Irish class structure the Uí Fidgenti were only middle tier among the ruling septs of the land, as they never contested for the kingship of the greater provincial kingdom of Munster, in which they were located. However, the Uí Fidgenti did not pay tribute to the Eóganachta kings of Cashel. The Book of Rights, transcribed as a medieval topographical poem set forth the rights of the O'Donovans: