Bank: down into the coal, up from the river

To most people, a bank is the sloped ground beside a river or stream. Water runs downhill; the bank is the solid edge where it stops. The word carries this sense of edge, margin, boundary. You stand on the bank and look across the water.

In coal mining, the bank is not the edge of anything. It is the working face: the wall of coal that miners are actively cutting and extracting. A miner works at the bank, driving picks and shovels into the exposed seam. The coal face recedes as you work it; the bank moves backward into the earth. This is where production happens, where the coal leaves the ground.

The two senses share a geometry of exposure. A riverbank is a vertical or near-vertical face where soil or rock meets water. A coal bank is a vertical or near-vertical face where worked coal meets the unworked seam. Both are surfaces, both are boundaries between two different states or materials. The word likely migrated from river geography to mine geography because miners and quarrymen saw the same structural fact: a face where you stand and work, where one thing ends and another begins.

Other trades borrowed the term for similar reasons. A loading bank in rail yards is a platform face where goods transfer between ground and wagon. A load bank in electrical testing is equipment that presents a simulated demand or resistance. The word spreads wherever there is a face, a barrier, a place where work concentrates. The riverbank came first; the mining bank generalized it.