The Post Office of the Republic of Ireland publishes a postal directory
which lists both the Irish and English names for all post offices in the
Republic. Unfortunately it (at least the version I bought in Dublin
about 1970) does not list post offices in Northern Ireland.
The townland is a very small geographic unit (usually between about 100
and 1000 acres) so there are many more placenames in the Townland Index
than in the Postal Directory. To make sense of what the original Irish
placename was you need (only) a little Irish. The army actually
employed some fairly sophisticated scholarly talent (like the character
in the play) though there were no doubt errors.
Somewhere some years ago I ran across a reference, which I have lost, to
a catalogue of (I think) 17th century Irish place names, and if anyone
can come up with the reference I will be grateful myself.
David W. Miller
Professor of History
Carnegie Mellon University
David.W.Miller@andrew.cmu.edu