leather strop
A strip of leather used for polishing the edge of a blade, especially a razor or knife, after sharpening on a stone.
剃刀を研いだ後、革砥で仕上げる。
After sharpening the razor, I finish it on a leather strop.
Compound of 革 (kawa, 'leather') and 砥 (to, 'whetstone' or 'polishing'), referring to a leather tool used for polishing blades.