Brid,
Griffiths Valuation for 1860 lists just one Denis Farnan in Tyrone, and he was in the parish of Drumragh. He had a property in New St, Omagh. There is one death in the Omagh area of a Dennis Farnan in 1879 aged 90, so of the right sort of age. The informant was a John Farnan of Beagh. Dennis was a pensioner and so had probably served in the army or navy.
https://civilrecords.irishgenealogy.ie/churchrecords/images/deaths_returns/deaths_1879/06518/4877589.pdf
Beagh family in 1901:
http://www.census.nationalarchives.ie/pages/1901/Tyrone/Loughmuck/Beagh/1745950/
And 1911:
http://www.census.nationalarchives.ie/pages/1911/Tyrone/Loughmuck/Beagh/874499/
Charles Farnan was in court a number of times, often for drunkenness. (As reported in the Tyrone Constitution). One newspaper case attached.
Drumragh RC’s baptism & marriage records only start in 1846, so it will be hard to find information on Denis or Lewis due to the lack of records.
I found this Probate abstract in which I see that Patrick Farnan of Beagh was also known as Farnand. It doesn’t take much of a step to get from Farnand to Ferdinand. So possibly this is your family.
Farnan otherwise Farnand Patrick of Beagh Omagh county Tyrone farmer died 25 March 1892 Administration (with Will) Londonderry 23 February 1927 to Thomas Farnan farmer. Effects £103 2s. 6d. Patrick was born c 1810. The will should still exist, in paper format in PRONI.
https://civilrecords.irishgenealogy.ie/churchrecords/images/deaths_returns/deaths_1892/06036/4719101.pdf
The tithe applotment records for 1830 list a Patrick Ferron farming in Beagh, so it seems fair to say the spelling of the name varied a bit over the years. Not uncommon in Ireland as you may know:
http://www.irishgenealogyhub.com/tyrone/tithe-applotment-books/parish-o…
Another probate abstract for that family:
Farnan Michael of Beagh Omagh county Tyrone farmer died 4 December 1926 Administration Londonderry 9 March to Thomas Farnan farmer. Effects £63 12s. 9d.
