halberd
釶 centers on a type of polearm: a halberd. This is a specific weapon meaning with no broader conceptual cluster.
釶 combines 金 (metal) with 也, which likely contributes a phonetic element. The character is used for a metal halberd, but its exact historical development is uncertain.
The left side is metal 金, and the right side 也 looks like a blade on a long shaft. Picture a metal halberd with a distinctive curved blade.
For シ, imagine a shiny metal halberd: the first sound of 'shiny' cues シ, and the weapon gleams in the light.