sword
鋘 centers on a bladed weapon: a sword. The meaning is narrow and concrete, with no clear abstract extensions in the given glosses.
鋘 combines 金 (metal) with 吳, which likely contributes the sound. The character is used for a type of sword, fitting the metal radical.
The left side is metal 金, and the right side 吳 looks like a complex shape. Picture a metal sword with an ornate hilt shaped like the 吳 component.
For カ, imagine a sword so sharp it can cut through a car: car -> カ, and the metal blade slices it cleanly.