Coming from a British perspective, none of the names given to aircraft carriers seem especially fanciful. Many British battleships and cruisers were given similar names; the Leander class, Arethusa class and all but three of the Dido class cruisers were named for mythological figures, while the battleships Resolution, Revenge and Valiant and cruisers Enterprise, Despatch and Dauntless were named for abstract concepts. Many of the names given to British carriers can be seen in this tradition.

Many of these ships had been named for illustrious predecessors. Ark Royal was named for the British flagship during the Spanish Armada, as well as for the first ship built by the RN as a specialised aircraft carrier. Hermes was the eighth ship to share the name; her immediate predecessor in the name was a cruiser converted to serve as the RN's first seaplane carrier. Some of the American ones had similar names. Ranger was named for a famous ship of the same name during the American War of Independence, the first command of John Paul Jones (the Essex-class carrier Bon Homme Richard was named for one of his later commands). Wasp and Hornet were both named for ships that served with distinction during the War of 1812, while Enterprise's namesake had fired the first shots of the First Barbary War. Most of the remaining American carriers were named for battles; three were named for founding fathers, and one for naval aviation pioneer Samuel Langley. The only standout was the Shangri-La, named as part of a joke about the Doolittle Raid, after Roosevelt suggested that the bombers participating in the raid had been launched not from a carrier, but from a base in the fictional Himalayan valley of Shangri-La.

I'm not sure if I'd call the WWII carrier names "fanciful" -- let's consider a short list.

USS Langley (CV-1): named after the naval aviation pioneer Samuel Pierpont Langley

USS Lexington (CV-2): named after the battle of Lexington as well as several fairly undistinguished previous USN ships

USS Saratoga (CV-3): named after the battle of Saratoga and other USN ships

USS Ranger (CV-4): named after the 1777 USS Ranger, a sloop commanded by John Paul Jones in a very successful series of commerce raids against the British. Ranger here is a nod to ranging over the seas.

USS Yorktown (CV-5): named after the battle of Yorktown and other USN ships

USS Enterprise (CV-6): named for several previous Navy ships, the first of which was captured from the British by the tiny Continental Navy; the most decorated USN ship of WWII and the namesake for CVN-65 and the PCU CVN-80

USS Wasp (CV-7): named for the stinging insect and after several other USN ships

USS Hornet (CV-8): named for the stinging insect and after several other USN ships

USS Essex (CV-9): named for several previous USN ships and eventually the county of Essex, in Massachusetts

USS Yorktown (CV-10): named for CV-5, which was sunk at Midway

Looking down the list of Essex-class carrier names, the only on that I'd really call "fanciful" is USS Shangri-La, which has a fun origin story -- FDR told reporters that the B-25s that bombed Japan in 1942 had flown from "Shangri-La," the mythical Himalayan utopia from the 1933 novel Lost Horizon.

To get to the actual question, though, the names of aircraft carriers were a bit up for grabs in the early days of aviation. In the USN, in the run-up to World War II, battleships were given state names (with the logical conclusion around 1900 or so that we'd need a fleet of 48 battleships, one per state) and cruisers were generally given city names or territory names. The Langley was a converted collier, while Lexington and Saratoga were converted battlecruisers that were allowed to be turned into carriers as a result of a rearmament treaty. Ranger was the first purpose-built carrier in the USN, and naming it for Jones' ship was a nod to the possible commerce-destroying mission of aviation (no one really knew what to do with carriers at the dawn of naval aviation).