My ancestor, Mathias Breen (b. 1832) was from Kilofin parish in Co. Clare. His mother was a Morony from Kilmihil parish. He emigrated with his sister Margaret in 1851. In 1853 a person names "John Cunninn" of Braggville, Mass. ran a Boston Pilot ad searching for information about Mathias and his sister. I have never been able to find out who this "John Cunninn" was or how he related to the Breens. The name "Cunninn" is found virtually nowwhere else, and several people have suggested to me that it is likely a misprint (the result of the ad submission being written in illegible longhand perhaps?) and that the person's name was likely Culligan, or Cullinan, or Callaghan (all 3 being names that appear in 1800s records in Clare).
Kilrush is quite close to the Kilofin peninsula where my Breens originated, so I'm wondering if, by any chance, you've run across any Breens (or Moronys) connected to your John William Culligan (b. 1848). He obviously wouldn't have been old enough to the the John who ran my Boston Pilot as, but I'm just looking at other people near the Breens with names similar to "Cunninn" which I do believe was not his correct name.