Berba: the Barrow, a river in Leinster
Bercha: on or near the Shannon, near Bellanagare, in East Roscommon
Berchna: probably for Bercha
Bernas: the pass cut by Medb from Louth into Armagh; probably the "Windy Gap" across the Carlingford Peninsula
Betha: see Sliab Betha
Bir: the name of several rivers; probably Moyola Water, a river flowing into Lough Neagh
Bithslan: a river in Conalle Murthemni
Blai: a rich Ulster noble and hospitaller
Boann: the River Boyne
Bodb: the father of Badb