Japanese ship names follow different conventions from those typical in the West. Merchant ship names often contain the word maru at the end (meaning circle), while warships are never named after people, but rather after objects such as mountains, islands, weather phenomena, or animals.
The word maru (丸, meaning "circle") is often attached to Japanese ship names. The first ship known to follow this practice was the Nippon Maru, flagship of daimyō Toyotomi Hideyoshi's 16th century fleet.
Several theories purport to explain this practice:
Today many commercial and private ships are still named using this convention.
When the Imperial Japanese Navy was formed, the Ministry of the Navy submitted potential ship names to the Emperor for approval. During the early years ships were often donated by the Shogunate or Japanese clans and the original clan names were kept.
In 1891 the procedure was changed due to changes in the government structure. Two ship names were submitted by the Minister of the Navy to the Lord Chamberlain who then presented the choices to the Emperor. The Emperor could either pick one of the suggested names or one of his own devising.
Ships captured during the First Sino-Japanese War kept their original names but with Japanese pronunciation. For example, the Chinese battleship Chen Yuan became Chin'en in Japanese service.
In 1876 the Minister of the Navy was given the authority to choose the names of torpedo boats without imperial approval. In 1902 the authority to name destroyers was delegated to the Minister of the Navy as well.
In 1895 a proposal was made by the Minister of the Navy in an attempt to establish some standard. He proposed that battleships and cruisers be named for provinces or shrines dedicated to protecting Japan, that names of other warships be selected from the names for Japan or provinces.
Ships captured during the Russo-Japanese War were renamed with Japanese names. Some of these vessels were given names related to where they were captured or some other aspect of the war, such as the month of capture. Some Russian ships were given Japanese names that were phonetically similar to their original Russian names (example: Angara became Anegawa).
In 1921 the Minister of the Navy was given authority to name all ships except battleships, battlecruisers, and cruisers. In any event the Navy had to report the new name to the Emperor immediately.
On 23 April 1905, Naval Minister Gonbee Yamamoto reported to the throne about a new ship naming standard. It was decided on 1 August 1905.
However, second class and third class cruisers ended up with river names because it became complicated.
It passed through some changes afterwards, the broad categories of names are given here, with examples, however, if the name is the succession to a ship's name, it is excluded from following contents.
Prior to the end of World War II Japanese ship names were rendered in kanji; after the end of the war this tradition was abandoned in favor of hiragana to separate the perception of the Maritime Self-Defense Forces from the old navy.
The English translations of the Japanese warships provide names; the literal translation of the characters does not necessarily represent how the name is perceived to the Japanese. For example, Akagi is probably perceived as "red castle" by Japanese about as often as Philadelphia is perceived as the "city of brotherly love" by Americans.
There is a tendency for translations of Japanese names to be somewhat fanciful. For example, Shōkaku is often translated as "crane flying in heaven", but "flying crane" or "soaring crane" is a more accurate translation. Another fanciful translation is "land of divine mulberry trees" for Fusō—fuso was a Chinese name for a mythical tree supposed to grow to the east, hence an old poetic word for Japan.
In World War II, the composition of the Japanese Navy was a military secret. US Naval Intelligence built up knowledge of enemy ships through photographic reconnaissance, interrogation of prisoners, and signal interception. Inevitably there were mistakes and misinterpretations; some of these have been repeated in post-war accounts that rely on US Navy documents. For example, a prisoner of war after the battle of Midway reported the existence of an aircraft carrier named Hayataka. This was a misreading of the characters 隼鷹 in kun-yomi, while they in this case are properly read in on-yomi as Jun'yō. Accordingly, many US documents refer to the carrier as Hayataka or its class as the Hayataka class. In another example, when Joseph F. Enright claimed the sinking of the Japanese Aircraft Carrier Shinano, US naval intelligence was originally only willing to credit him with sinking a cruiser; this was in part because they believed the name "Shinano" (derived from intercepted Japanese transmissions) referred to the Shinano River (thereby denoting a cruiser), when in fact the name referred to the Shinano province of Japan. (Shinano had begun construction as a Yamato-class battleship and was thus named for a province, before being converted into an aircraft carrier following the Battle of Midway.)