This sounds very interesting!! Ellen is a name that is prominent in my family.... I don't know about any Horrigan kin in Killorglin, and in fact, the last time I looked into it, it was a dead end in terms of finding ANY Horrigans, Horgans or Harrigans in Killorglin....but more information is always becoming available!
Have you used the IGI provided by our Mormon friends? I found my McCarthys there.