Of course the term FIDI, which seems to be coming into very limited use, and which might have been applicable decades ago, is rather pointless now- with the current geographic spreading of New York’s finance industry: to Brooklyn (Metrotech Center), New Jersey (largely Weehawken) and midtown Manhattan (as along Sixth Avenue).
There is no point in trying to rename the old financial district from “Wall Street”, which retains geographic reference, to a meaningless trendy-sounding bi-syllable.