It was most often said by an adult, and - at least in our home - frequently delivered in a teasing manner toward a child suddenly shy around newcomers.
Or perhaps it was delivered in a chiding tone, when you were caught doing something you shouldn’t?
The McGraw-Hill Dictionary of American Idioms and Catch Phrases defines it as “A fanciful explanation for a person’s silence or refusal to speak.”
The phrase isn’t all that old, actually.
Its dates back to the mid-1800’s, both in the U.S. and England. Word Wizard chased it back to 1859, in an article in an Illinois newspaper:
“To this I made no answer. I loved a rainy day, too, but I was not disposed to say so just then. ‘Oh no! The cat has got your tongue has it?’”
Maxwell wonders whyever anyone would think a cat would want a human tongue, when he already has a perfectly serviceable one?
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Sources:
Jacksonville Journal Courier (Illinois), 23 January, page 2.
McGraw-Hill's Dictionary of American Idioms and Phrasal Verbs, Richard A. Spears, McGraw-Hill, September 1, 2003.
GrammarPhobia
WordWizard
Phrases.org: Cat Got Your Tongue?
