In solo games, I usually take the default names. In PBW games, it has not happened often to me yet that human players could see a fleet of mine long enough for me to worry, usually when they see it , it hits them the next turn
Nevertheless, when I started playing PBW I was paranoid about humans figuring out by the name of the ship type what the ship did. (for instance, in solo play a minelayer would be called "Minelayer".)
I found refuge in my native tongue, Dutch. I use Dutch slang to disguise a ship function, though I still usually call them by their function, especially non-combat ships.
This makes for some odd translations of for example a Point-Defense ship. And sometimes Dutch is too similar to english. (for example, guess what a "Garage" ship does). Also, in the PBW games that I just created (see other thread) or just started playing in, I have roughly the same opponents as in my first round of PBW games. So I guess the Dutch won't work anymore.
My attack ships: I have always used the "ravager.txt" file for this, cause I like to have attack classes like "Dominator" , "Conqueror" or "Abomination". Unfortunately too many AI races use the same txt file and they use up the available names way too fast. (they won't call an upgraded BLaster a BLaster II).
I use the roman numerals for upgrades until a human player has seen what a BLaster (x) ship is, then I change names.
I don't usually name ships individually.
At the end of my Last PBW game I started using fantasy names instead, borrowed from the Jordan and Tolkien books. So I'd have Gargoyle classes, Trollocs, Draconians and Myrrdaals. Bigger hull size means bigger monster name. My single baseship was called "Dark One".