In Ireland, the word culchie is used to describe anybody one perceives as being more rural than oneself. Thus, Dubliners apply it indiscriminately to anybody living outside the Dublin metropolitan area, regardless of whether this person might live in one of the country's other cities. Outside of Dublin, urbanites will use it to refer to anybody with a connection to the land, and most specifically, any rural dweller with an impenetrable country accent. The word is most likely a corruption of some form of the word "country".
Growing up in Limerick city, I am naturally considered a culchie by most "Dubliners". What is ironic is that most of those people who have applied this term to me in the past dwell in the furthest suburbs of Dublin city, often in neighbouring counties, and visit the city centre only rarely, while I spent my entire childhood in an urban environment. Of course, there should be no stigma attached to being a denizen of the countryside, but it amuses me that Dubliners tend to have such a distorted mental picture of the rest of the country.