This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
傹 combines the person radical 亻 with 竟, but the exact historical development and original meaning are uncertain.
A person 亻 beside 竟, a shape that appears in boundary and mirror kanji. Without a clear meaning, picture a person standing at the edge of something undefined.
For ケイ, imagine a person 亻 standing at the edge of a boundary 竟, holding a key: key -> ケイ, though the meaning is unclear.