Translation according to P. W. Joyce:
Pollnabrone in Galway; Poll-na-bron, hole of the millstone or quern. See vol. i. p. 376 [reproduced below].
A quern or hand mill is designated by the word bro, which is also applied to the mill-stone used with water mills; genitive brón or bróin [brone], plural bróinte [broanty]. We find this word in the names of several places, where it is likely there were formerly water mills or hand mills, the owners of which made their living by grinding their neighbours' corn. Coolnabrone, the hill-back of the quern or mill-stone, is the name of two townlands in Kilkenny; and in the same county near Fiddown, is Tobernabrone, the well of the quern; Clonbrone and Cloonbrone, the meadow of the mill-stone, are the names of some townlands in King's County, Galway, and Mayo. Before the potato came into general use it was customary for families - those especially who were not within easy reach of a mill - to grind their own corn for home consumption; and the quern was consequently an instrument of very general use. We may presume that there were professional quern makers, and we know for a certainty that some places received names from producing stones well suited for querns. Such a place is Carrigeenamronety, a hill near Ballyorgan in Limerick, on whose side there is a ridge of rocks, formerly much resorted to by the peasantry for quern stones; its Irish name is Carraigín-na-mbróinte, the little rock of the mill-stones; and there are other rocks of the same name in Limerick. So also Bronagh in Leitrim, i.e. a place abounding in mill-stones.