I did search the Tithe Appointment Book and there are only two John Nevin in Lissonuffy Parish in 1825.
There were a group of people in Ballyscully 49 in Galway Tynagh Parish in 1826. Not sure if anything is relevant.
The Tithe Applotment books contain only a fraction of people, only those who held enough of the right sort of land which made them liable to pay tithes. None of my ancestors are in it. There are very few names in my ancestors' townlands in Tithe Applotment books compared to the number in Griffiths' Valuation.
A few reasons for the lack of people in Tithe Applotment books:
Tithes were levied on agricultural land; if your ancestor was a landless farm labourer or a servant or worked in a shop in town, they didn't pay tithes.
Land holdings had been subdivided so often among sons and then among their sons, that some land portions were too small to be considered.
Some sub-tenants paid their rent (or did work in lieu of rent) to another tenant. That tenant might be responsible for collecting rent from several sub-tenants and it was his name which was recorded in the tithe books, not the sub-tenants.
Re. list of people in Tynagh, County Galway. I doubt they are relevant unless you have other evidence that your ancestors were there. They are almost all common surnames + v. common forenames e.g. Malloy or Mally is one of the commonest names in Mayo. Tynagh is near Loughrea in Co. Galway, if it's the village I think it is.
https://registers.nli.ie/
Not sure which R.C. parish it comes under- perhaps Kilbride or Clontuskert?
I use Shane Wilson's website to match church parishes to places. His registration district finder is useful too. Website has an introduction to Irish FH and a guide to sources. Link in aghadowey's reply #73.
I also use the little map in the corner of a parish page on NLI Catholic Registers website, checking which are adjacent parishes to the one I'm interested in.