As the Irish were immigrating to America, like most newcomers in this new strange land, most were poorer than dirt. As ship after ship came to America from overseas, the Irish got numerous enough to form various sections, which today might be called ghettos and they lived in small homes that were not more than shanties. Some chicken coops might have been larger than the first homes of these immigrants.
As time went on, the Irish began to separate as to their degree of upward mobility. When some Irish moved up the ladder of success into larger frame houses for example, those still in the shanties saw this as taking on fancy airs, and they were dubbed "lace curtain."
The lace curtain Irish in turn, labeled their less fortunate countrymen as "shanty" or sometimes "pig in the parlor Irish." There were yet other derogatory terms used. They were tough times and the terms were annoying, regardless of which side of the tracks you might live on.
In many cases, the "lace curtain Irish" were as poor as the shanty Irish but they had their own notions that they were more respectable. When there was no frame house per se, some were called lace curtain simply because they would put up lace curtains for appearances' sake, even in a shanty town. Thus both the terms, lace curtain Irish and shanty Irish, are far from being compliments to any Irish. Yet, over time, as food and jobs became more plentiful, the Irish overcame their own labels and most today do not care whether they are shanty or lace curtain Irish.
Along with the terms shanty Irish and lace curtain Irish we have the terms "hoi polloi" -- a Greek term referring to "the many," i.e., the common people-- and hoity-toity, an adjective used to describe those who would have others believe they are elite and enlightened.
Many of us get the two terms messed up and often we would consider the lace curtain Irish to be hoi polloi, thinking it means people who think they are big shots. But, that is not the meaning of hoi polloi. The big shots, or big shot wannabes are the hoity-toity and if they are Irish, they would be of the lace curtain variety. The common folk, as in "we the people" or the many, are the hoi polloi and if they are Irish, they would be known as the shanty Irish. But, then again, who cares?
We are Americans!