Meaning

adjective thickly covered with ingrained dirt or soot

adjective (of color) discolored by impurities; not bright and clear; is often used in combination

adjective causing dejection

originFrom English dialectal (Kentish) dingy (“dirty”), of unknown origin, though probably from Middle English *dingy, dungy, from Old English *dyncgiġ (“covered with dung, dirty”), an umlaut form of duncge, dung (“dung”), equivalent to dung + -y, hence a doublet of dungy.

Etymology from Wiktionary, CC BY-SA 3.0