This question has come up fairly regularly on the newsgroup
	but has never been resolved definitively.  Neither "black"
	or "shanty" are used much in Ireland.  They seem to be mainly
	used in America.

	"Shanty Irish" was used to describe the poorest of the poor
	Irish immigrants, the kind who ended up in shanty town (the
	origin of the word "shanty" is not known, but it might come
	from the Irish "sean tí", meaning "old house").  Today "shanty"
	in the States is a derogatory term for people who in Ireland
	might be known as culchies but the people so described need
	not necessarily be of Irish descent.

	"Lace curtain Irish" could be as poor as the Shanty Irish but
	they had notions of being more respectable.  They were called
	that because they would put up lace curtains for appearances
	sake, even in a shanty town.  Thus the term is far from being
	a complement.

	{ Thanks for clarification to Neil Cosgrove. }

	"Black Irish" is often taken to mean Irish people with dark
	hair and eyes.	One romantic story is that they are the
	descendants of shipwrecked sailors of the Spanish Armada.
	Unfortunately for the story, it is very unlikely that enough of
	the sailors survived for their genes to be in the population
	visible today.	A variation on this theme says they are
	descended from Spanish Moors who traded with people on the
	west coast of Ireland.	Another explanation is that it's
	common in Irish to give people nicknames based on their hair,
	such as Seamus dubh and "black Irish" is just a carryover of
	this into English.  Some people say that the "black Irish"
	were the original inhabitants of the island and all the rest
	were just blow-ins.

	One other interpretation is that "black Irish" refers to the
	descendants of Irish slaves taken to the Caribbean island of
	Montserrat during Cromwell's time.  The descendants of these
	slaves and black slaves from Africa live there to this day.
	The surprising thing is that they still speak with an Irish
	accent!