"Jim, O'Bore is a mondegreen for Abore and Mary Flynn is a common name". Abore"
Careful about making definitive statements Susan - too many problems with that one. As far as I'm concerned, the first stop in all this is the information you have immediately at hand.
The singer, Frank Feeney, from Leopardstown, South Dublin (home of the famous horse races) gives the information that "She was a lady Eagar out of Blessington, out of Glending" - Blessington is in Wexford - south west of Dublin.
According to 'Joyce's Place Names', just over the border in Co. Carlow, is a townland named Both or Bough, giving its name to 'Rathbough, among other local features - literally 'Hill of the Cow'.
Taking all these facts together - I am tempted to guess at Lord O'Bore = Lord of Bore = Lord Of Bough (possibly pronounced Baugh) - by no means definitive, but a clue to the rationale of the singer - maybe.
If Frank Feeney had been a non-literate Traveller, either this, or Burr, in County Offaly, would have been my strong guess.
It is dangerous to arrive at definitive explanations for these things.
Jim Carroll