While the final rann remains as much as puzzle as the previous
two, I have had few more thoughts about it.
Êirni dar cêill ertha tuir,
tabair a rêir, a lâich lir,
adledh do lâmh tech na muc
nî da râd dún rut, a fhir.
>>> Êirni dar cêill ertha tuir,
> érnid (< as·ren) = pays, dispenses, bestows
> ernaid = bestows, grants
> "you grant beyond reason"
If, however, we read "dar" as the contraction of "do + ar =
to/for our", we would have "you bestow on our reason/mind"
(cf. "ernid etaige do bochtu" = he bestows clothes on the
poor). We can further take the verb "érnid" in its second
meaning "unriddles, solves, explains, makes clear", we get:
"You make clear to our mind..."
The next two words, "ertha tuir" are still opaque to me,
although the syntax suggest that they *could* be a noun phrase,
perhaps a plural noun followed by an adjective or another
noun in the genitive. "Tûir" could possibly be the genitive
of "túr = seeking, searching, investigating".
For "ertha" I'm pretty much flailing around, as far afield as:
ertha = értha = áertha = past part. or gen. of vn. ???
For the next line, "tabair a rêir, a lâich lir", Neil suggested:
> Give its tribute, o warrior of a host,
Since "tabair" can mean either "give" or "take" depending on
the context, I would suggest that "take its reward (for making
something clear)" might fit better here.