I have a Catherine Cummings in my tree who was married to Richard McNeilley (various spellings). They first appear in the 1861 census in Douglas and they are both listed as born in (Northern) Ireland, as are a reasonable proportion of Cummings/Cummins in the census indexes, in Ramsey and Douglas.

I don't know an awful lot about the Cummings and wondered if there could be a connection with yours, unless they are definitely Scottish.