Hopefully you've worked this part out but just in case........
Reengarorga is 'Reengarorga Island' or even spelt 'Ringarorga Island'.
The spelling does vary.
It is just near Rath (Rathmore), Tullagh
So its off the Skib to Baltimore Road but just outside of Baltimore.
There's a nice stone bridge joining it to the mainland.
There are various parts to the Island including Donegal, Inane, Gortnalicky, Gortaliscaw and Gortadrohid. These are used in the 1901/1911 Census as 'Townland' and the DED (electoral division) as Cape Clear.
Some residents had their birth place recorded as 'Baltimore' rather then Rath or Reengarorga.
Various Leonard families were found on the Island and around Rath (and still are).
The catholic church at Rath is St Mary's and the local pub is the 'Sibin' which I believe Michael Collins used to frequent.
The area had many fisheries and I believe a larger population in the late 1880's to 1930's.
My family immediate and ancestral families are from the area and I've obtained documents via the Skibereen Heritage Centre.
Hope this is of interest.
Padraig