Green’s Dictionary of Slang

a reply that silences one’s opponent.

c.1499		Skelton Bowge of Courte line 477: I have a stoppynge oyster in my poke.
1542		Udall (trans.) Erasmus’ Apophthegms (1564) Bk I 61: To a feloe laiyng to his rebuke, that he was ouer deintie of his mouthe and diete, he did with this reason giue a stopping oistre.
1546		J. Heywood Proverbs I Ch. xi: His wyfe to make up my mouthe, / Not only her husbandes tauntyng tale avouthe, / But thereto deviseth to cast in my teeth, / Checks and chokyng oysters.