“FiDi” is a name that was used in 2006 for the financial district. The term FiDi is borrowed from San Francisco’s Financial District.
     

Google Books
Frommer’s San Francisco 2005
by Erika Lenkert
Hoboken, NJ: Wiley Publishing, Inc.
2004
Pg. 239:
Though locals don’t frequent this Fi-Di (Financial District) place, it’s very popular with tourists.
     
Google Groups: ba.food 
From:  A. Sears
Date:  Thurs, Nov 2 2000 5:00 pm
 
I haven’t been there yet, and I’m still trying to figure out what the relationship is between Bistro Zaré on Polk, Zaré on Haight, and Zaré in the Financial District (on Sacramento near Sansome).  I’ve only eaten at the one on Sacramento and was very pleased.  I seem to remember that there are two Zaré brothers - the gregarious Hoss Zaré of the FiDi location and the unknown-to-me <?>

Zaré.  Which one owns/runs the other two Zarés, and whether either is as good as the FiDi location, is a mystery to me. 
 
My Midday Stroll
Tuesday, December 12, 2006
My Midday Stroll
In New York City, there exists an area known as “The Financial District.” More commonly known as the “FiDi,” this area is home to the city’s brightest, most attractive, and best paid individuals. The FiDi is the cultural epicenter of New York City.

And within this epicenter, there is an epi-epicenter: 85 Broad, Goldman Sachs’ main offices. This is where our story takes place.