The term "Knickerbockers" traces its origin to the Dutch settlers who came to the New World - and especially to what is now New York - in the 1600s. Specifically, it refers to the style of pants the settlers wore...pants that rolled up just below the knee, which became known as "Knickerbockers", or "knickers".
In 1809, legendary author Washington Irving solidified the knickerbocker name in New York lore when he wrote the satiric A History of New York from the Beginning of the World to the End of the Dutch Dynasty under the pseudonym Diedrich Knickerbocker. Later known as Knickerbocker's History of New York, Irving's book introduced the word "knickerbocker" to signify a New Yorker who could trace his or her ancestry to the original Dutch settlers.