俵鋲 Tawarabyou Rice Bale Rivet
What is Tawarabyou in Japanese Katana terminology?
Originally, it was a type of ""Menuki"" (rivet), a rivet used to secure the shark skin, etc., wrapped around the handle (Tsuka) of the Tachi Koshirae (sword fitting). It is driven from the blade side of the handle, and a seat is inserted on the back side to secure it. As the era changed and the Tachi Koshirae became stylized and more decorative, the rivets on the front and back began to be driven separately.
In the early Edo period, this decorative metal fitting began to be simplified, and items with an oval rivet head carved with lines imitating a rice bale appeared, which came to be called "Tawarabyou".