noun
tonoko; polishing powder; clay powder
A fine powder made from dried clay, traditionally used for polishing wood, metal, or lacquerware, and as a filler in crafts. The term is often used in woodworking and restoration contexts.
木地に砥の粉をすり込んで磨く。
Rub tonoko powder into the wood surface and polish it.
漆器の下地に砥の粉を使う。
Tonoko is used as a base filler for lacquerware.
Compound of 砥 (to, 'whetstone') + の (no, possessive particle) + 粉 (ko, 'powder'). The reading とのこ is a sound shift from と + の + こ.