A comment made when someone is unaccountably or unusually quiet, as in We haven't heard from you all morning—has the cat got your tongue? Often put as a question, this term originally was used mainly with a child who did something wrong and refused to answer any questions. Today it is used more generally to ask anyone to speak. [Mid-1800s]
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.