I believe Nollaig refers to just the Christmas season (as in "Nollaig shona dhuit!" the greeting used by Gaelic speakers to wish another person a merry Christmas, but it's been about four years since I took Gaelic and very few people I have lasting contact with in Milwaukee speak Gaelic.)
You could access
http://www.irishmilwaukee.com for more information and get a "quickie" lesson in Gaelic online, complete with explanations and links to other sites.
Phyllis (aka Sidhe Uaine or Gaia Euphoria)