to cut meat off away from bones, ancient torture
叧 centers on cutting or separating flesh from bone, with an extended historical sense of a cruel punishment involving such cutting.
叧 is a rare character. It visually combines 口 and 刀, but the exact historical development is uncertain. It may have originally depicted a mouth and a knife, suggesting cutting or separating, but this is speculative.
A mouth 口 above a knife 刀: imagine cutting meat away from the bone with a knife, or the gruesome image of an ancient punishment involving cutting.
For カ, imagine a carver cutting meat: carver -> カ, and the knife 刀 separates the flesh.