I just came accross this site and it has come as a bit of a revelation.
I had always wondered where my surname originated and had been told conflicting stories. Some french people once told me the name was connected to DuClos but I had also been told the name was Irish. Your message has made everything clear now.
Coincidently my mother's side of the family all came from Cork so it is strange to find that my father's side have roots their too.