I am new to the study of Irish, particularly old Irish, and I've encountered a word, and a phrase, that I can't find a translation for online. So I'd very much appreciate some help.

The single word is "heclasta".

I have found it online in the phrase (from the Silva Gadelica):

"ótchonnaic in náidin mbic innti ro grádaig fó chétóir i ocus ro ail co heclasta || í ."

But, unfortunately, I'm also unable to translate most of that. All I can figure out is that it seems to say something about love, a (female?) child, and a grave.

Thanks.

co heclasta = go heaglasta = religiously

see: http://edil.qub.ac.uk/search?q=eclasda& ... n=headword
(voilá, there's even an almost identical quote: an naoidhin... is do oil go heaglusta í
So it is prob. the same story as in Keating’s Foras Feasa: http://www.ucc.ie/celt/online/G100054.html )

for Modern eaglasta see here: http://www.teanglann.ie/en/fgb/eaglasta

I too have a word which I am told is old Irish Gaelic and no longer used in modern Irish. The word is 'Bile' which refers to a sacred tree. As I am still working on getting a handle on Irish pronunciation I am not sure if this word would properly be pronounced BE-lay or Beel or something else. Can anyone help me with this?

/b′ɪl′ə/ like English "bill uh"

It rhymes with file /f′ɪl′ə/
http://www.teanglann.ie/en/fuaim/file

Ah, that makes sense. Go raibh maith agat.