If you have ever wondered why Long Island is called Islip, you're not alone. There are plenty of reasons for this naming convention, but there's also a bit of history behind it. First, Islip is a town in the Town of Islip, which is also the location of a census-designated place (CDP) named Islip. In the 17th century, the town was home to a large group of Algonquin Indians. Their subgroup, the Secatogues, occupied parts of Islip, Bay Shore, and Oakdale.