This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development is uncertain. It visually combines 判 and 鳥, but the component relationship is unclear.
The top part 判 suggests judgment or a seal, and the bottom 鳥 is a bird. Imagine a bird acting as a judge, but the real meaning is unknown.
For かけす, picture a bird (鳥) that makes a 'kake' sound while sitting on a 'su' (巣, nest): kake-su -> かけす.
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