inferior silk, tassel, fringe
紇 centers on low-quality silk and the decorative trimmings made from it: tassels and fringes. The idea is silk that is not fine enough for main fabric, so it is used for ornamental edges.
紇 combines 糸 (silk) with 乞, which likely contributes the sound. The exact historical development is uncertain, but the structure suggests a phono-semantic compound where 乞 indicates the reading and 糸 specifies the material.
The left side is 糸 (silk), and the right side 乞 looks like a person begging. Imagine a beggar wearing clothes trimmed with cheap, inferior silk tassels and fringes.
For コツ, think of the coarse, inferior silk as being full of 'knots' (コツ). The tassels and fringes are made from this knotty, low-quality silk.
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