Big Apple
"The Big Apple" was popularized as a name for New York City by John J. Fitz Gerald in a number of horse-racing articles for the "New York Morning Telegraph" in the 1920s. The earliest of these was a casual reference on 3rd May, 1921:
Barry Popik
Barry Popik (born 1961) is an American etymologist who is recognized as an expert on the origins of the terms "Big Apple", "Windy City", and "hot dog". He is a consulting editor of the "Oxford Encyclopedia of Food and Drink in America" and was described in "The Wall Street Journal" as "the restless genius of American etymology".