gate of a market
闠 refers specifically to the gate of a market, the entry point to a commercial area.
闠 combines 門 (gate) with 貴, which likely contributes the sound and relates to value or goods, fitting a market gate.
The gate 門 encloses 貴 (precious, valuable). Picture the entrance to a market where valuable goods are traded.
For カイ, imagine a buyer at the market gate asking, 'Can I buy?' — 'Can I' sounds like カイ, and the gate leads to the market.
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