Shimane Prefecture was formed by joining together 3 of the old provinces, Oki Islands, Izumo, and Iwami. The old provincial identities remain strong today, with an Iwami identity being stronger than a Shimane identity. I live in Iwami, and most of this blog is about Iwami.
The name Iwami is written with 2 kanji, "iwa" meaning rock/stone, and "mi" meaning look/see, so the name means something like "see rock".
The most common theory of the names origin says that it refers to the rocky cliffs around Hamada, which was the original provincial capital, but on one of my shrine-visiting walks I came across another story which is not well known, but far more interesting
The story begins a long, long time ago, before the introduction of Buddhism, when the area was ruled by female shamans.
The people of the area were under attack from a giant eight-colored serpent( not to be confused with the eight-headed serpent of Izumo).
The local kami, a shamaness names Amenotoyotarashikarahime fought against the evil serpent, and like all such battles it was long and hard, but the evil power of the serpent was too strong and eventually Ameno weakened.
Just as it looked as if Ameno would be defeated, "ofuda" rained down from the sky. Ofuda are small paper strips from shrines that are in essence charms to ward off evil or encourage good spirits. These ofuda were from a kami from neighboring Izumo, Yatsukamizuomitsununomikoto. (if Susano can be said to be the creator of the Izumo nation, and Okuninushi presided over it's demise, then Yatsukami ruled at the height of Izumo's power)
The ofuda did the trick, the serpent was weakened, and Ameno revived enough to finish off the serpent and hack its body to pieces. (North of here is a mountaintop shrine in the village of Yairoishi (eight-colored stone), and behind the shrine is the head of the eight-colored snake, now turned to stone)
The next part of the story is a little unclear, either for some reason Ameno turned herself to stone, or she turned the serpent, now in pieces, into stone. As the stone head exists, it seems likely that the latter is the story.
Anyway, Yatsukami felt the event was important enough that he instructed the people to remember the event by "LOOK AT THE STONE!"