Knickerbockers are short pants that go below the knee. Think old school baggy baseball pants. You know, the ones from when Ruth was playing. Or old golf pants. You could do an image search on Bobby Jones if you need help picturing them. They go slightly below the knee. The first organized baseball team was the New York Knickerbockers, named for their pants, but the Knickerbockers were an athletic club that would play various sports. Knickerbocker is also a Dutch last name, and Washington Irving wrote a book, The History of New York, which featured the fictional author Diedrich Knickerbocker. The pants actually got their name from the idea that aristocratic Dutch in New York wore them after they went out of style in favor of trousers. The point is, Knickerbocker as a name, the short pants, and athletic clubs have all been associated with New York for a very long time before the New York Knicks chose their name.