armour neck plates
鍜 refers specifically to armour neck plates, a protective piece of metal gear worn around the neck.
鍜 combines the metal radical 金 with the phonetic component 叚, suggesting a metal object whose name is related to the sound カ. The exact historical development is uncertain.
The left side 金 (metal) and the right side 叚 (which looks like a protective covering) together suggest metal plates shielding the neck.
For カ, imagine a car's metal frame protecting the neck area: car -> カ, and the metal neck plates are like a car's armor.
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