Carthage is a location on Earth, the home of historical military commander Hannibal and his army.
In 218 BC, Hannibal's Carthaginian army marched for Italy, where they were defeated by the forces of the Roman Empire. (TOS comic: "No Time Like the Past")
Carthage also existed on Magna Roma and was conquered by the Magna Romans. (TNG novel: The Captains' Honor)
Federation starships named USS Carthage are called as such in honor of this location and its history.