Hi Allyson
I have a copy of a booklet titled 'Offaly Tombstone Inscriptions; No. 4 - Daingean Graveyards', a 1985 publication of the Offaly Historical Society (ed. John Kearney), which lists all the inscriptions of Killaderry graveyard plus the Church of Ireland gravestones. There is no record of a Sherwood but there is a 'Pain' monumental stone from more than 200 years ago, so it may be a link with a change of spelling over the years. It is lengthy so I will only give the names here - erected by Catherine, and mentions John Denny (her father, d 1811), his father Peter of Ballylakein (d 1793), her brothers Bernard and Lancelot. If it is the right family, that will be a good addition to your tree. There are more than 150 headstones recorded, and probably 300 or more names. It also includes the story of Fr Andrew Mullen who is buried there, a revered local man who died at 28 in 1818.
It's a pity that the old cemetery has been let go. I remember going there in 2000 while staying nearby and it was in reasonable shape then. I have two of my gt gt gt gt grandparents buried there.
Good luck
Bernard