From Japanese Destroyer Captain, by Tameichi Hara (Naval Institute Press, 2013), Kindle Loc. 537-564:
Names of Japanese ships must sound strange to foreign readers. Many Westerners during the Pacific War called a Japanese ship “Maru.” It must be noted, however, that warships or other government ships do not have names ending with Maru. Maru has always been and still is used only for merchant ships or fishing boats.
Maru literally means circle, round or chubby. In medieval Japan, Maru was frequently used for childhood names of boys. For example, in his childhood Hideyoshi Toyotomi, the famed warlord of the 16th century, often considered Japan’s Napoleon, was called Hiyoshi Maru, which may be translated literally as “chubby (or lucky) sunny boy”; and as a youth Yoshitsune Minamoto, the great 12th century general, was called Ushiwaka Maru, meaning “healthy and strong as a calf.”
The Japanese people, by way of personification, came to add Maru to ship names. In the last 100 years Maru has been dropped from the names of all government ships. Japanese warships, like those of other nations, are classified so that all ships of a given type have names of the same category. Hence anyone familiar with the system can tell at once from its name whether a ship is a battleship, cruiser, destroyer, and so on.
Japanese battleships were always named after ancient provinces or mountains. Famed Yamato was christened for the province of Japan’s most ancient capital city, Nara, in Central Honshu. This word was also used in ancient times to mean the whole country of Japan. This may explain the close attachment felt by the Imperial Navy for the greatest battleship ever built. Her sister ship, Musashi, was named after the province immediately north of Tokyo. Exceptions to this practice are Haruna and her sisters—Kirishima, Kongo, Hiei. Originally classed as battle cruisers, and named for mountains, they retained those names even after they were reclassified as battleships in 1930.
Heavy cruisers were traditionally named after mountains, and light cruisers were given the names of rivers. Carriers usually bore poetic names having to do with flight. Hosho, the world’s first keel-up carrier, built in 1921, means “Soaring Phoenix.” Hiryu and Sory[u], of the Pearl Harbor attack, may be translated “Flying Dragon” and “Blue Dragon,” respectively. Kaga and Akagi, which perished along with the two Dragons at Midway in June 1942, are exceptional names for carriers because Kaga is a province and Akagi a mountain. The explanation is that these ships were converted from a battleship and a cruiser.
Submarines and sub-chasers had only numbers. Large submarines had the letter “I” for a prefix, while, the numbers of smaller ones were prefixed by “RO.” The numbers of sub-chasers were prefixed by the letters “SC.”
First-class destroyers were given meteorological names such as Hatsuyuki (First Snow), Fubuki (Blizzard), Shimakaze (Island Wind), Amatsukaze (Heavenly Wind), Akitsuki (Autumn Moon), Fuyutsuki (Winter Moon), or Yugumo (Evening Cloud). Second-class destroyers were named for trees, flowers, or fruit such as Sanae (Rice Seedling), Sakura (Cherry) or Kaba (Birch).
When a Japanese warship was scrapped, a new one often inherited the old name, but without any signifying numeral like “II.” Thus I served in two different ships named Amatsukaze.