Translation according to P. W. Joyce:
Gortnacross in Galway; Gort-na-croise [-crusha], of the cross. Here the incorrect nom. cross is kept, instead of gen. crusha : p. 12 [reproduced below].
Nominative incorrectly used for Oblique Case. During my examination of thousands of place-names, I have observed one circumstance that ought to be brought prominently under notice. When the genitive or other inflected form of a noun forms part of a name - especially if that noun be in familiar colloquial use - the people, when pronouncing the whole anglicised name, often reject the inflected form and restore the more familiar nominative - even though it is incorrect, and though the native Irish speakers, when uttering the Irish name, pronounce it correctly, using the inflected case, not the nominative. For example, eas, a waterfall, is sounded nom. ass, but gen. assa; so that Letterass, in Mayo, should have been anglicised Letterassa, where assa correctly represents the genitive (Leitir-easa, hill side of the waterfall). But ass was more familiar, so they adopted it wrongly. Even a more striking instance is using bro (nom.) for brone (gen.), a millstone or quern; as we see in Knocknabro, in Kerry, the hill of the quern, which should be Knocknabrone, as it is in Waterford. This is a principle of wide application, for there are many other cases of violation of grammaatical rules in anglicising, to which I will often direct attention as we go along. Sometimes these departures from grammar seem to get mixed up with the principle enunciated from Professor MacNeill (at p. 14, below), so that in case of some individual names it is not easy to say under which they fall.