“The Natural History of the New Japan Islands” writes that over the years, a number of historians, biologists, and linguists have puzzled over the etymology of the name “minoshiro”, and come up with a few interesting theories.
An old accepted explanation was that its name came from the fact that looked like it was wearing a raincoat.1 But the book doesn’t say what kind of raincoat, and I’ve never seen one before, so I have no idea whether this explanation is accurate or not.
Another reason came partly from the cape-clad appearance, and partly from its white color, combined with the belief that the souls of the dead lived within it.2 Also, the fact that the minoshiro is usually terrestrial, but returns to the sea to lay eggs was a plausible origin for its name.3 A later explanation was that the red and yellow eggs that it laid in clumps of seaweed or coral resembled ornaments in the palace of the Dragon King.
Another unofficial reason came from the fact that the when it faced an enemy, the minoshiro’s tail will bristle and stand straight up, like a shachihoko4 found on the roofs of castles in the ancient past. They named it after the castle in Mino, but later research showed that the it was Nagoya Castle that had shachihoko, which was in the neighboring province of Owari. After that discovery, the explanation lost its appeal.
There are also numerous stories saying that “shiro” is the name Shirou shortened. Since Shirou was just over a meter tall, he was called Minoshirou (“mino” is three times the length of a standard-width cloth, around 108 centimeters). A different story said that once he met a snake-like creature with numerous tentacles, which also gave him the name Minoshirou.5 The stories are varied and hard to get a grasp on.
Still on the topic of Shirou, one old folktale says that he was cursed by a white snake and turned into a minoshiro. Since other details of the story were lost, there is no way to prove its authenticity.
Personally, I think any of the stories are possible. At least it is much easier to understand compared to the etymology of the name of the toads that are everywhere on Mt. Tsukuba. In the book it says that “it uses powers to draw in and devour insects”. Who would believe the idea that toads have canti?
2 The kanji is 蓑白 (minoshiro), ‘straw cape’ plus ‘white’, which turned into 霊の代 (minoshiro) ‘soul’s substitute’.
3 The kanji is 海の社 (minoshiro), which I think means ‘shrine of the ocean’
5 Snake can also be written 巳 (mi), so Minoshirou would mean ‘Shirou of the snake’. Also I think the snake it’s talking about is Orochi