mound, bud
碚 centers on a raised heap of earth or stone: a mound. The bud sense is a rare extension, possibly from the idea of a small rounded protrusion like a mound.
碚 combines 石 (stone) with 咅, which likely contributes the sound. The character is rare, and its exact historical development is uncertain.
The left side 石 means stone, and the right side 咅 looks like a sprout 立 above a mouth 口. Imagine a stone mound with a bud sprouting from its top.
For ハイ, picture a high mound of stones: high -> ハイ, and the mound rises up like a high pile.
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