the.com/burnisher

means A hard, smooth tool (often steel, agate, or bone) used to polish metal, leather, or other surfaces by rubbing them under pressure until they gleam.

from From 'burnish,' borrowed from Old French 'burniss-,' a stem of 'burnir'/'brunir' meaning 'to make brown or shine' — itself tied to 'brun,' meaning brown. The logic: polished metal was described by its darkened, glowing hue before 'burnish' narrowed to mean the shining act itself. The '-er' was simply bolted on to name the tool that does the rubbing.