means The act of making a blade, point, or edge keener by grinding or honing away material — or, figuratively, refining something until it cuts more effectively.

from From 'sharp,' which traces back to Old English 'scearp,' meaning keen-edged or cutting, with cousins across the Germanic family — Old Norse 'skarpr,' German 'scharf' — all circling the idea of something that bites. The '-en' makes it a verb of becoming (as in 'harden,' 'lengthen'), and '-ing' freezes that becoming into an ongoing act. So the word is literally 'the making-keen,' a process older than written English itself, born wherever someone first dragged stone against metal.