A traditional Japanese mortar, often a large wooden or stone device operated by foot or water power, used for hulling rice or pounding grains.
In old farmhouses, they used a mortar to hull rice.
An Edo-period stamp mill is on display at this museum.
唐 (kara, 'Chinese') + 臼 (usu, 'mortar'). The exact historical derivation is uncertain, but the term likely refers to a mortar design introduced from China.