Oops, meant to add a bit more before the message popped off!
I believe the association with Navan is likely to the fort, and Navan being an ancient "capital" of Ulster. They sing in "Ulter" or Donegal dialect, and some in the band have taken a workshop from Lillis O Laoire (according to their now somewhat out of date website). Lillis is currently the foremost academic authority on Donegal sean nos. He teaches at the University of Limerick's World Music Centre, if I remember correctly.