This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
僟 combines 亻 (person) with 幾, which likely contributes sound. The exact historical development is uncertain.
A person 亻 beside 幾, a shape associated with 'how many' or 'almost'. The meaning is unclear, so treat it as a person near something uncertain.
For キ, imagine a person asking for a key to unlock the meaning of 僟: key -> キ.