blade, sword, edge
刄 centers on a sharp cutting tool: a blade, sword, or edge. It is a variant form of 刀, carrying the same core idea of a knife or sword.
刄 is a variant form of 刀 (knife, sword), with an additional stroke that may have originally indicated the blade's edge or a decorative variation. The exact historical development is uncertain.
The shape resembles a knife with a small mark on the blade, highlighting the sharp edge. Think of it as a sword with a notch that makes the blade stand out.
For ジン, imagine a sharp blade cutting through a piece of denim jeans: jeans -> ジン, and the blade slices the fabric cleanly.