This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
牱 is a rare character composed of 牜 (cow) on the left and 可 on the right. The exact historical development is uncertain, and it may be a variant or a specialized character with limited usage.
Since the meaning is unclear, focus on the shape: a cow 牜 beside 可. Imagine a cow that can (可) do something, but what it does is uncertain.
For カ, imagine a cow (牜) that can (可) say 'kaa' like a crow: kaa -> カ.