The USN usually followed naming conventions in the past, but not much anymore. Aircraft carriers were named after famous battle victories (Midway) or famous political figures (Roosevelt), battleships after US states (New Jersey), cruisers after US cities (Newport News), submarines after fish (Dogfish) and destroyers and smaller ships after famous naval figures (Leahy). The ship I spent the most time on was the USS Harry E. Yarnell, a guided missile frigate named after some obscure admiral. Of course, the crews of every ship have their own nicknames too. We affectionately called the Yarnell the "Hairy Urinal".