cover of tripod cauldron
鼏 refers specifically to the cover or lid of an ancient tripod cauldron. It is a rare, specialized character with no broader conceptual extensions.
鼏 combines 冖 (cover) with 鼎 (tripod cauldron), directly depicting a lid on a cauldron. The historical development is straightforward and well-supported.
The top component 冖 looks like a lid, and the bottom 鼎 is an ancient tripod cauldron. Together they show a cover placed over the cauldron.
For ベキ, imagine a heavy lid that makes a 'beki' sound when it clangs shut on the cauldron. The invented sound 'beki' cues ベキ.
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