rough geta; rustic wooden clogs
Refers to a type of geta (traditional wooden sandals) that is roughly made, often from Japanese cedar, giving a rustic or simple appearance.
旅館の庭に出るとき、山下駄を履いた。
When I went out into the garden of the inn, I wore rough geta.
Compound of 山 (yama, 'mountain') and 下駄 (geta, 'wooden clogs'). The exact origin is uncertain, but it likely refers to geta worn in mountainous or rural areas, or to their rough, simple construction.