tire of wheel, band
釭 centers on a metal ring or band that fits around something, specifically the outer tire of a wheel. The idea is a circular metal reinforcement or binding.
釭 combines 金 (metal) with 工, which likely contributes the sound and may suggest a crafted object. The character refers to a metal band or tire, fitting the metal component.
The left side is metal 金, and the right side is work 工. Imagine a metalworker crafting a strong metal band to fit around a wheel.
For コウ, picture a metal band being hammered into shape with a loud 'ko' sound: コウ echoes the ring of metal on metal.