The original song was written by a woman called Mary Ward (about whom I have been unable to trace anything) and titled 'A New Song on Davitt's Lover's Lament on his incarceration from the banks of the Moy'. I think the song contains a good deal of poetic licence (or biographical ignorance). As far as is known, Davitt only ever had one 'lover': his wife Mary Yore, whom he married on 30 December 1886.
Prior to this he had spent many years in jail, firstly for Fenian activities, later for Land League 'agitation'. As far as I can learn, his prison record was,
1870-78 Newgate, Millbank, Dartmoor.
19-25 November 1879 Sligo Jail.
3 February 1881-6 May 1882 Portland (in Dorset).
8 February 1883-4 June 1883 Richmond Bridewell, Dublin.
The original ballad refers to 'young Peter Crawley from Kilcoody that died in Kildorney also'. I haven't been able to trace this person or these places. There are tho very similar place names in County Cork and the Fenian Peter Crowley was killed there in 1867.
When I visited the Davitt Museum in Straide, Mayo, a few years ago I also got a copy of a poem called 'Michael Davitt'. It isn't very good but as it was written by a local National School teacher, M.J. Flanagan, in 1906, I'll post the words later (it's quite long). The Museum didn't have a copy of the original ballad so I gave them one.
In 1908, Davitt's first biographer Francis Sheehy-Skeffington called him 'the greatest Irishman of the nineteenth century'. I still think that's true.