to pierce, to stab, to take
鈌 centers on penetrating or thrusting into something: piercing, stabbing, or taking by force. The meanings share the idea of a sharp, invasive action.
鈌 combines 金 (metal) with 夬, which likely contributes the sound and may relate to the idea of piercing or breaking through. The exact historical development is uncertain.
Metal (金) on the left and a shape like a sharp tool (夬) on the right: imagine a metal spike piercing through a surface.
For エツ, picture an etching tool made of metal piercing a plate: etch -> エツ, and the metal spike stabs into the surface.