quiver, arrow holder, (kokuji)
笂 centers on a container for arrows: a quiver or arrow holder. It is a kokuji created in Japan for this specific object.
笂 is a Japanese kokuji formed by combining 竹 (bamboo) and 丸 (round), suggesting a round bamboo container for arrows.
Bamboo 竹 is woven into a round 丸 shape to make a quiver: 笂 holds arrows.
For うつぼ, imagine an arrow quiver made of bamboo that is so full it looks like a round 'utsubo' (a type of eel-like fish) – the shape and name both fit: うつぼ.
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