Explanation:
New York City is America’s largest city and one of the most popular in the world. The city is home to some of the world’s most historic monuments, magnificent buildings, and countless dazzling skyscrapers. For centuries, New York has been an <em>urban jungle</em> and <em>epicenter for art</em>, <em>dining</em>, <em>shopping</em>, and <em>trendy neighborhoods</em>. New York has been nicknamed the "Big Apple," although the name has no reference to the growing of apples. The nickname the "Big Apple" <em>primarily gained relevance in the 1920s through horse racing</em>, as reported in the New York Morning Telegraph by John J. Fitz Gerald. Prior to this, the city referred to as the "New Orange," nicknamed after William III of Orange, the Dutch leader who conquered the English and took over New York.
Origin of the "Big Apple" Nickname
Various myths existed regarding the origin of the name, including a reference to the people who sold apples on the streets to earn a living during the Great Depression. However, other accounts claim the name originated from a woman named Eve who ran a brothel was referred to by her girls as "Big Apples." However, the name is believed to have originated from a precept used by newspaper sports columnist John J. Fitz Gerald in the New York Morning Telegraph. On February 18, 1924, Fitz Gerald officially nabbed the colloquialism in his articles under the heading “The Big Apple.”
Fitz Gerald had heard the name being used by two African-American stable hands to refer to the New York City, whose horse racing trails were deemed the most preeminent venues. Once the name became popularized, it spread beyond sports into nightclubs and music. In 1930, jazz artists from New York took on the term to refer to their hometown in their music, popularizing the name further to the northeast.
Use in Popular Culture
The moniker soon languished from use until the 1970s, when it was revived as part of a campaign in hope of reviving New York’s tourist economy. <em>During that time, the city was in economic distress, coupled with intensified street crime that tarnished the city’s image.</em> In the hopes of restoring the city to its former glory, Charles Gillett, president of the New York Convention and Visitors Bureau, promoted the city as the "Big Apple," and used there image of the apple on t-shirts, placards, and promotional materials. This time, the nickname stuck.
In 1997, the corner of West 54th Street and Broadway, where Fitz Gerald had lived between 1934 and 1963, was named "Big Apple Corner" in his honor. In 2016, President Donald Trump hosted a party to celebrate his victory and named it the 'Big Apple Ball' with decorations and cut-outs of New York landmarks in honor of his home city.
Today, the nickname is ubiquitous with New York City throughout the English-speaking world
Site:
https://www.worldatlas.com/articles/why-is-it-called-the-big-apple.html
(You may find some more interesting facts there. I have laid out only the important facts)