First off, don't call a Traveller a "Gypsy." It's a derogatory word, and just about the most offensive way you can possibly refer to an Irish Traveller. Only the word "pikey" might be worse, but that only happens in Britain. "Knacker" is another well known derogatory term. Some Travellers today are significantly more offended by "knacker" than "gypsy". Older works might call them "Tinkers," from the fact that a lot of them used to be itinerant tinsmiths. This is also considered offensive. The proper word is "Pavee," not that you'll hear it used much.