"dead credit" isn't a concept, it is a metaphor. See the notes: "Verse commentary in Polish presents mourning over the personalized credit (buying on credit I warn you, do not go anywhere without money - Przestrzegam was nie chodźcie nigdzie bez pieniędzy):"
The community are mourning the loss of credit. I'm not sure what event caused them to lose credit privileges, but the cartoon is treating death as a metaphor for loss. There is also an obvious, irreverent reference to the Lamentation over the dead Christ.
The peasants, who had traditionally constituted a vital part of the town merchants' clientele, now impoverished and forced by their feudal masters to limit their purchases to what was produced or sold within their home estate, largely stopped plying their role in the internal market. The market became confounded further by the monetary crisis, warfare destruction and the fact that some of the most major Poland's and Lithuania's municipal centers were lost to the neighboring states, either permanently or at times of reversals of military fortunes. wikipedia
I think if I had infinite time, I'd research this as evidence of the role of consumption and credit in early capitalist economies.