Etymology and distribution of 下山井.

Shimoyamai 【下山井】^{レベル1
Very rare}  The Japanese surnames etymology dictionary.

Toyama-ken Nanto-shi · Kanagawa-ken . Summary . The first element "Mushi" stands for Takebe. Toyama-ken Nanto-shi Meiji New surname by monk of Senzoji Temple in Sangdong. In the same temple tells that it means "a legitimate species of the Takebe family." 武部 Takebe reference.