Hi Andrew, I live in Louth but about 25 miles or so from Killanny but have no local knowledge. I have looked at the 1901 census and the only family Corrigan in Killany are in Sandfield, father Patrick and wife Rose. This is free online here https://www.census.nationalarchives.ie/ which you are probably aware, it defaults to 1911.
McKenna is a common enough name in Monaghan and the parish of Kilanny is in both Louth and Monaghan, you are in the correct part, there is a map here of civil townlands (sometimes parish sizes and names differ) https://www.townlands.ie/
Irish genealogy is free online and should give you the civil registers for the births, marriages etc from 1864, birth records only to 1924 and marriages to 1948 and deaths to 1972 I think. https://www.irishgenealogy.ie/
The catholic parish records are also online, but Killany stops in 1880 for baptisms, https://registers.nli.ie/parishes/0314
There are a few Louth Facebook groups dealing with Genealogy and one with DNA matching using Gedmatch, not overly active but well moderated.
This site about Louth has a list of grave for which inscriptions are available, if any interest you let me know and I will see if I have them. https://www.jbhall.clahs.ie/connolly_-_coyne.htm
I am rushing off but please revert if you have any follow up, I agree about the use of words at the time but it was common, in some census you see people listed as "imbecile" and other names.
Regards
Pat
