The book you want to track down via your local library for Irish place name stuff if Irish Names of Places by P.W. Joyce. This is a three volume work and should not to be confused with the tiny Irish Placenames by the same author.

The latter is a new paperback and just contains a selection of names and possible/probable meanings. The original three volume edition has essays about the derivations and discusses a lot more. I've just got hold of a copy of this, so if there's anything I can look up just let me know and I'll see what it says. Sadly, the work was never completed, so there are quite a few gaps in there.