I usually use the irish place names site to check on the naming conventions for irish places.http://www.irish-place-names.com/
I think I created the Pettigo one.
There are many places that are both towns, townlands and parishes so I try and link them all together as often you might only have one name but by investigating the others that are connected you might find more family. This is particularly relevant for townlands which can be a very small geographic area.
For Pollans the Irish place name site lists, it as a townland, in the barony of Kilmacrenan, parish of Conwel, poor law union of Letterkenny as indicated already. So I would create the category for Pollans as follows:
[[Category: Townlands in Donegal]]
[[Category: Kilmacrenan, Donegal]]
[[Category: Conwel, Donegal]]
[[Category: Letterkenny, Donegal]]
You would then need to link them to the appropriate level above if they dont exist already. Ie Letterkenny to Poor Law Unions in Donegal etc.