The word Taig is a word used to describe Roman Catholic Irish people. Normally it is used in a derisive manner. Increasingly though, it is being used in an ironic, tongue-in-cheek manner and can actually be quite affectionate when used in the right context - but only when people from Northern Ireland use it with each other. That's not saying that I could walk into a pub and expect friendly embraces from all around if I were to announce I was going to buy all the Taigs a drink! Well ... having said that - if a drink is involved, maybe I would get embraces! lol
Anyway .. the word comes from the commonly found Irish surname, which is still found today in surnames like McTeague etc. Not half as common now as it once was.
The word Hun I'm not sure about... I suspect though that its obviously something to do with Attila the Hun and his tribe who went and conquered all before them.
The word Fenian, I think, comes from one of the Gaelic tribes who invaded Ireland around 400AD called Feni.