Cappagh for townlands is in many counties, there are 55 of them!!
In 1858 there were two McNicholas living in Sligo.
Patrick McNicholas, Parish Achonry, Townland Coolrawer
Poor Law Union Tobercurry, tenant of Edward John Nolan
7d house and 1/4 share of 44 acres 1 rood 35 perches
Patrick McNicholas, Parish of Kilshalvy, Townland Kilshalvy, PLU Boyle, tenant of Mrs. Hannah P. Weir
13a house, outbuilding and land 54 acres 1 rood 31 perches
The above is possibily the father of John born 1866 or grandfather, same for below:
John McGuiness, Parish of Easky, Townland Shannons Park West, Village of Easky,PLU Dromore West, tenant of Thomas Burke
James McGuiness, Parish of Easky, Townland curraghna Gap, Village of Easky, PLU Dromore West, tenant of Bridget Hale
Couldn't find any births for John McNicholas in Sligo
18 March 1866 #0504, Kiltamagh Mayo
1 April, 1866 #502 Kiltamagh, Mayo
16 July 1866 #0502 #0114 Balla, Mayo
I seem to remember a change of a civil district change of Sligo to Mayo, but not sure when that occurred.
John James registered birth April-June 1896, Tobercurry
Jane registered birth April-June 1896 Tobercurry
Peter Francis registered birth April-June 1896 Tobercurry
Elizabeth McGuiness birth registered 4 June 1870 Fa: Edward
and mo: Mary Mooney (Betsy short for Elizabeth)
Elizabeth McGuiness birth register 4 June 1870 Fa: James
McGuiness & mo. Catherine McKevitt (common to call Elizabeth Betsy)
James McGuiness 04 April 1879 Cappagh, Sligo Fa: Thomas McGuiness Mo: Beesy Bruen McGuiness
Needs more lookin
There is one McNicholas listed in the Sligo telephone book in Strandhill, Co. Sligo addresses sufficient for mail delivery. 1 McGuiness in Mayo, 0 in Sligo.