The name means the northern, shady side of the mountains in contrast to the yang "southern, sunny" San'yō region to the south.

[5] The eastern part of Shimane Prefecture also had cultural and economic connections to the Asian mainland from an early period.

[4] The San'in region corresponds to San'indō (山陰道), one of the gokishichidō, or five provinces and seven circuits established in the Asuka period (538–710) under the Ritsuryō legal system.

[7] The San'in encompassed the pre-Meiji provincial areas of Tanba, Tango, Tajima, Inaba, Hōki, Izumo, Iwami and Oki.

The daimyō regional rulers used the San'indō for their sankin-kōtai mandatory journeys to Edo (modern Tokyo).

In modern Japanese usage it generally refers to the prefectures of Shimane, Tottori and northern area of Yamaguchi.

Per Japanese census data,[11] and,[12] San'in subregion has had continual negative population growth since 1992.