Etymology and distribution of 井の下.

Inoshita 【井の下】^{レベル2
About 20}  The Japanese surnames etymology dictionary.

Kagawa-ken , Hyougo-ken · Oosaka-fu . Kagawa-ken Zentsuuji-shi Distributed in Zentsuji Town.

Variant of accompanying (van). It was in Shiga-ken during the Kamakura period. The pronunciation is van. 伴 Ban reference.