I don't know if you have looked at the census on line at National Archives Ireland. Its a free service and there are several Maddens listed in King's County. If you just do a search for Madden with no first name you will come up with several options. There were, in fact, Maddens living close to my home place, Kilcoursey, Clara, Co Offaly (King's Co) when I was a child....a long, long, time, ago. Let me know how you're doing with the search. Regards.
This is zany. I live in Offaly (formerly Kings County) and from where all my ancestors originated. I am currently researching my family history. I will check with older friends to see if I can find a Coy or Cory sounding place here. Meantime, best regards.
Welcome to this vast club of searchers. Perhaps your folk originated in GOREY which is County Wexford. If you use the LDS site you might locate some information. Also you might like to try the Wexford Family History site. I believe they are on line. Good luck.