CVN

The larger concept here is the U.S. Navy’s “hull classification system.” The Navy needs to keep track of its ships, so each one has a “hull number.” This is a code for the type of ship, then a number. No two hull numbers repeat for ships in active service.

Some common hull type designations:

• BB: battleship (obsolete; we don’t have battleships anymore)
• C*: some type of cruiser (which is very vague; more below)
• D*: some type of destroyer

Note that the general naval classification of ships has been historically vague. Cruisers are commonly considered the heaviest combat ships in modern times, while destroyers are smaller, but I couldn’t find much common ground for the term “frigate.”

Wikipedia concedes as much:

After World War II, a wide variety of ships have been classified as frigates. Often there has been little consistency in usage. While some navies have regarded frigates as principally large ocean-going anti-submarine warfare (ASW) combatants, others have used the term to describe ships that are otherwise recognizable as corvettes, destroyers, and even nuclear-powered guided-missile cruisers. Some European navies use the term “frigate” for both their destroyers and frigates.

For whatever reason, the Navy uses the “C” prefix designation for aircraft carriers. Cruisers are very large heavy warships, and the first carrier might just have been a re-purposed cruiser, or considered to be a cruiser based purely on size, before carriers became a classification all their own.

The Navy then adds a “V,” so the hull number for every aircraft carrier starts “CV.” Most resources claim the “V” stands for “voler,” which is French for “to fly.” I couldn’t find any reason why the Navy decided to use a French word here, but several resources did note that “CA” was already in use, so they logically had to pick something different.

As for the third letter in an aircraft carrier hull number, there have been quite a few over century, which changed based on the evolving role of the carrier. Fast-forward to today, and we only have one left: “CVN,” where the “N” means “nuclear.”

There are no non-nuclear carriers remaining in active service, so the “N” serves no real purpose anymore – it is vestigial.