A clam is any bivalve mollusc known to quickly close its shell when it feels threatened. When people refuse to talk because they feel anxious or in danger, they are said to “clam up”, that is to shut their mouths tight just like the mollusc closes its shell.
“Clam” in inglese significa “mollusco bivalve”, “vongola”; questi molluschi chiudono velocemente la propria conchiglia quando si sentono minacciati. Il verbo “clam up” si usa per indicare l’azione di chi si rifiuta di parlare perché in ansia o in pericolo e quindi tiene la bocca ben chiusa. Una metafora simile in italiano potrebbe essere “chiudersi a riccio”.
E.g. He flushes and I worry that he’s going to clam up, but he keeps talking.
