the.com/leach

means To have a substance gradually drawn out or filtered away by liquid passing through, or to drain something that way yourself.

from Traces back to Old English 'leccan,' meaning to moisten or water, part of a Germanic family of words tied to wetness and dripping (a relative of 'leak' is often suspected but not firmly proven). The chemistry/mining sense — liquid trickling through material and carrying off its soluble bits — developed later, as people noticed rain and water doing exactly that to soil, ash, and ore.