"
Joisey" is the way some New Yorkers mispronounced New Jersey (both leaving out the "New" and pronouncing "Jersey" badly). People who moved to New Jersey from New York and who
prided themselves in not having the extreme accent of some people in their
old New York neighborhoods would sometimes ridicule and imitate the way these New Yorkers referred to New Jersey as "Joisey." These days, some people from other parts of the country, or at least not from New Jersey, mistakenly think that "Joisey" is the way New Jerseyans commonly refer to their state.