Redorer son blason (literally "to re-gild one's coat of arms") was a social practice taking place in France before the French Revolution, whereby a poor aristocratic family married a daughter to a rich commoner.
On the other hand, the commoner was allowed to add the aristocratic name of his bride (with the nobiliary particle "de") to his own family name, and this was dearly sought.
[5] As the French economy underwent drastic changes after the Middle Ages, many aristocratic families lost their position of power and wealth, and ended up in poverty.
For those aristocratic families from the provinces and far from Paris, far away from power and its associated gratifications, redorer son blason was often the only way to remain afloat.
[6] An example of this contemporary usage in French newspapers is the Le Point headline: "Les maires FN veulent redorer leur blason".