I only just found out that Douglas Hyde, a most dedicated philologist specializing in the Gaelic, became the first President of Ireland....and that at a most advanced age. I want to find out more about him. But that is another subject.

I posted his six-verse translation into English, a post or two back on this thread. Hyde was one of the founders of The Gaelic Journal, which printed the Gaelic original of this poem in its volume IV in 1893, six years before Hyde published his translation; I suspect a direct connection there. The Gaelic Journal, in printing an original Gaelic version eight pages in length, credits manuscript C 88 at what is today the National University of Ireland, Maynooth, for its source.
More than one copy exists of this poem, it appears in a number of manuscripts. In one manuscript, don't know which one, it has nine verses. The Maynooth version has eight verses.

Here are the six verses, in the original Irish, corresponding to Douglas Hyde's English translation earlier in this thread.

Truagh mo thuras ar Loch Dearg
A Righ na gceall is na g-clog!
Do caoineadh do chneadh is do chréacht,
'S nach dtig déar tar mo rosg.

Gan súil dfhliuchadh a ruisg,
Iar ndéanamn gach uilc dá mhéid,
Le chroidhe nach iarran acht síth,
Mo thruagh! a Rí, cad do dhéan?

Gan tuirse croidhe, gan maoith,
Gan doilgheas ag caoi mo locht;
Níor shaoil Pádraic, ceann na gcliar,
Go bhfaghadh sé Dia mar so.

Aon-mhac Calphuirn, ós dá luadh,
Och, a Mhuire, is truagh mo chor!
'S nach feacaidh an feadh do bhí beo
Gan lorg na ndeor ar a rosg.

I gcaraidh cumhang cruaidh cloch,
D'éis a ndearnas d'olc is d'uaill,
och, is truagh nach faghaim deor
Is mé adhlaicthe beo san uaigh.

A Aoin-mhic lér cumadh cách
'S nár sheachain bás na dtri ndealg!   
Le croidhe nach cruaidhe cloch
Is truagh mo thuras ar Loch Dearg.