timber, lumber, woodcutter, (kokuji)
杣 centers on wood from a mountain: timber, lumber, and the woodcutter who works with it. As a kokuji, it was created in Japan to express this specific mountain-forestry idea.
杣 is a Japanese kokuji formed by combining 木 (tree) and 山 (mountain) to represent timber or a woodcutter working in mountain forests.
A tree 木 on a mountain 山 is the source of timber. Picture a woodcutter felling trees on a mountain slope to produce lumber.
For そま, imagine a woodcutter in a mountain forest saying 'So, ma!' as he starts his work: 'So, ma!' -> そま, tying the sound to the mountain timber scene.
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