Starships Class designations take their names  from the first ship of the series. So before there as an Enterprise-D there was an U.S.S. Galaxy. Before there was a TOS Enterprise there would have been a U.S.S Constitution. Before Voyager there was a U.S.S. Intrepid. I wonder what the stories of these ships are. No doubt there are books to be recomended about some of them.