Translation according to P. W. Joyce:
Clynagh in Galway; Cladhnach, a place full of mounds or ramparts : termination (full of) added to Cladh : p. 12, I [reproduced below].
We have a great many ordinary Irish terminations, for the most part denoting the same as the English terminations ous and ly, namely "abounding in", "full of". The chief ordinary Irish terminations are ach, lach, nach, rach, trach, tach, seach, chair. For all these and others, see vol. ii. p. 3 [the part pertaining to nach follows]. Nach: usual anglicised forms, nagh, ney and ny. This postfix is well exhibited in Lougharnagh, a townland near Galway bay in the north-west of the barony of Kiltartan, anciently one of the seats of the family of O'Heyne: for the Irish form we have the authority of Mac Firbis (Hy F. P. 68), who writes it Luacharnach, meaning rushy land, from luachair, rushes. Another very good illustration is Sawnagh, the name of a place near Portumna in Galway; Samhnach, a place abounding in samh [saw] or sorrel. Bracknagh, Brackenagh (vowel sound inserted - page 3), and Brackney, the names of many places in various counties, same meaning as Bracklagh - a speckled place (from breac). In the parishes of Lackagh and Rathangan in Kildare, there are two townlands called Mynagh; and in Meath, Tyrone, and Cavan, there are several places called Moynagh; all meaning a level place, from magh, a plain; while with the diminutive, the name becomes Moynaghan (small level spot) near Irvinestown in Fermanagh. From mothar [moher] a thicket or a ruin of a building, comes Mohernagh near Shanagolden in Limerick, a place of thickets or ruins. In the parish of Moynoe in Clare, four miles north of the village of Scarriff, there is a mountain called Turkenagh, the name of which is derived from torc, a boar, and signifies a resort of wild boars; like Muckenagh, from muc, a pig, Brockenagh, from broc, a badger (see these in 1st Vol.). Exactly in the same way is formed the name of Ushnagh Hill, in the parish of Conry in Westmeath, celebrated in ancient Irish history - the point where the provinces met, and where King Tuathal the Acceptable built a palace and established a fair in the first century. In the oldest authorities the name name is spelled Uisnech, which comes from os, a fawn (inflected to uis by a well known orthographical rule, just as it is in the proper name Oisin), and signifies a place of fawns. The Dinnseanchas indeed accounts for the name differently (see O'Curry - Lectures, I. 191); but the story there told is quite worthless as an authority, so far as the etymology of the name is concerned. There is another place with this name, now called Usnagh, in the parish of Clogherny in Tyrone.