hatchet, adze
釿 centers on a cutting tool with a blade set at a right angle to the handle: a hatchet or adze, used for shaping wood.
釿 combines 金 (metal) and 斤 (axe), suggesting a metal axe-like tool. The exact historical development is uncertain, but the component combination fits the meaning of a hatchet or adze.
The left side 金 is metal, and the right side 斤 is an axe. Picture a metal axe head attached to a handle: that's a hatchet or adze.
For キン, imagine a king using a golden hatchet to shape his throne: king -> キン, and the metal axe is in his hand.