It comes from the Hiruzen highlands in the north of Okayama. In the 1950s and 60s, households up here made their own miso as a winter keeping-food and used it in their fried noodles, which was ordinary domestic cooking and not a specialty of any kind whatsoever.

Then a restaurant in Hiruzen built a sauce out of that. Miso as the base, with garlic, onion, apple, and various other ingredients and seasonings worked into it, until the result was something distinctly its own.

They fried that sauce with oyadori, mature hen meat, and cabbage, and put it on the menu. That particular combination is the thing that eventually became known outside the area.

Both of those choices are unusual ones. Fried noodles almost everywhere else use pork, and this uses old laying hens instead, which are tougher to chew and far more flavorful for it. The cabbage comes off the Hiruzen plateau itself. The sauce is invariably described as secret, which presumably means that every shop mixes its own version and not one of them will say what is in it. What the whole of this dish rests on is the miso that families up here were already making anyway, to get themselves through the winter.