Daikanyama (Daikan Mountain)
First a quick definition. A 代官 daikan was a kind of local magistrate or governor in the Edo Period.
There are 2 theories as to why this area is called Daikan Mountain:
1) A daikan‘s residence was located here at some time.
2) The forest mountain here fell under the direct supervision of a daikan.
There is insufficient documentation remaining to support one theory over the other.