This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
觽 combines 角 (horn) with 嶲, which likely contributes sound. The exact historical development is uncertain.
With 角 (horn) on the left and a complex right side, 觽 looks like an ancient horn tool or ornament, but its exact use is unclear.
For ケイ, imagine a horn-shaped key unlocking a mysterious box: key -> ケイ, and the horn 角 hints at the shape.