To dispose of family heirlooms or valuable possessions, typically to raise money or pay debts.
To sacrifice or give up something valued or emblematic of a family's heritage or dignity for short-term gain.
2.
British Englishgeneralfigurativepejorative
To betray or compromise an institution, tradition, or long-standing interest by selling off, dismantling, or relinquishing prized assets or principles.
Examples:
EN: And if you're going to sell the family silver to the Indians, consult the bloody Foreign Secretary!
ES: Y si vas a vender la plata de la familia a los Indios... ¡consulta antes a la maldita Secretaría de Asuntos Exteriores!
EN: It's one thing, as Macmillan said, to sell the family silver.