Though he himself was cursed to be a wanderer, Cain founded a city, which he named after his son, Enoch or Hanoch. The early Mormons apparently had this city in mind when they used Cainhannoch as a code name for New York.
In the original Hebrew, the name Cain is written with three letters: קין, usually romanized as QYN (or, with the unwritten vowels added, Qayin). The q represents not the “kw” sound of English, but a uvular stop, something like a “k” sound articulated farther back in the throat, and is sometimes transliterated as k or c. So the Hebrew spelling of Cain could be romanized as CYN (a Greek root which, like the Latin canis, means “dog”) — or, since Hebrew is written right-to-left:
NYC is New York City — a.k.a. Cainhannoch, the city of Cain. The “Big Apple” nickname also connects it with Abel, which sounds like apple.
The Cain/dog connection is also relevant to New York. Canine is sometimes written as K-9, and K is the 11th letter of the alphabet — giving us 11-9, or the 11th of September.
Shortly after 9/11, a prophecy falsely attributed to Nostradamus was circulated on the Internet:
In the City of God there will be a great thunder,
Two brothers torn apart by Chaos,
while the fortress endures,
the great leader will succumb,
The third big war will begin when the big city is burning
Nostradamus didn’t really write it, but all of it except the fifth line was in fact written before 9/11 (in a 1997 research paper by Neil Marshall) and is fair game for interpretation as a prophecy, or at least as a significant coincidence. Much of the interpretation is obvious — the “two brothers” are the Twin Towers, the “fortress” is the Pentagon, etc. — but it’s less clear why New York should be called the “City of God.” The NYC/CYN connection clears things up, though: CYN means “dog,” so God (dog spelled backwards) maps to NYC. New York as the city of Cain and Abel also adds another level of meaning to the “two brothers torn apart.”