Use the older names from Ships of the Line and 4th and 5th rate Frigates!
*Aside* Out of my boredom with work and my studies, I have started reading books on the early royal navy and pirating in the 16th to early 18th centuries. Lots of inspiration!
Bret BSs are named after counties. It's already been said. They don't follow the same convention as todays Royal Navy, which doesn't really have a convention, save it has to sound dramatic.