What is the meaning of the word maru in the names of Japanese boats?

"Maru" in a ship's name
Photo credit: Ciro Cattuto / CC licence

The names of many Japanese merchant vessels such as Nippon maru (日本丸) and Shonan maru (昭南丸) end in maru (), a Japanese word meaning "round". The earliest recorded instance of a ship with this name ending is the Bandou-maru (坂東丸) recorded in a document of the Niwaji (仁和寺) temple in 1187, during the Heian era (794-1185).

The word maru was also used in infant names of boys, yōmyō, yōmei (幼名), such as Ushiwakamaru (牛若丸), the infant name of Miyamoto no Yoshitsune (源義経), in the names of swords, such as Onimaru (鬼丸), one of the Imperial treasures, and parts of Japanese castles called kuruwa.

The origin of the maru in the names of boys is said by some to have come from a Japanese word for excrement, maro, or from potty, o-maru, in an effort to ward off demons by giving the child an unpleasant name. Another explanation is that it came from the similar maro (麻呂,麿), as in the name of the famous Ukiyo-e artist Utamaro (歌麿).

For the names of boats, multiple explanations have been proposed since the Edo period (1603-1867), including that it comes from the boy's name ending maru, or from the name ending maro (麿) used for objects of affection, or from the logs, maruta (丸太), used to build the boats, or from the round, tub-like shape of early vessels, or from the name of a Chinese figure, Hakudoumaru (白童丸), said to have descended from heaven and taught shipbuilding, or from the name of wholesalers, once known as monmaru (問丸), the "maru" of whose name was then transferred to the boats, or from the castle-like nature of the ships.

Names ending in maru were popular during the Edo period (1603-1867), and a Japanese shipping law of 1900 (Meiji 33) said "船舶ノ名称ニハ成ルベク 其ノ末尾ニ丸ノ字ヲ附セシムルベシ" (As far as possible, ships should be given names ending in the character "maru".)

Jim Breen's original answer
In the 1905 edition of Basil Hall Chamberlain's "Things Japanese" he says of maru "It is often asked: what does the word Maru mean in the names of ships ...?" His answer is:


This answer was originally contributed by Jim Breen, but has since been heavily edited.

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