The story
From make a silk purse of a sow's ear, with the common perception of swine as unrefined, dirty, or base creatures.
Etymology from Wiktionary, CC BY-SA 4.0.
you can't make a silk purse of a sow's ear
Today it means: It is not possible to produce something refined, admirable, or valuable from something which is unrefined, unpleasant, or of little or no value. Full definition →