Nutty, I wrote a song called "Billy Reilley" which I used to sing with the harp around the folk clubs when I performed with Packie Byrne. Various people picked it up, and a friend reported to me that it was introduced - in all good faith, I'm sure - by a singer as being a traditional song from the Famine era! In fact it only dates back to 1979, and deals with a young man of that name who leaves Ireland as part of the great exile after the terrible defeat at Limerick. The girl character who is narrating the song summons him back, and therein lies the tale. And every verse does end with the echo, "Billy Reilley".
Is this the one you meant? I plan to re-record this song before too long. Let me know if it is and I can type it out. But if anyone is singing it or putting it into DigiTrad, PLEASE credit me as the author because I did write it!
All the best, Bonnie