"HAS THE CAT GOT YOUR TONGUE? Why don't you speak? Your silence is suspicious. The saying originated in the mid-nineteenth century and was used when addressing a child who refused to answer a parent's questions after some mischief. Often shortened to `cat got your tongue?'." From "Random House Dictionary of Popular Proverbs and Sayings" by Gregory Y. Titelman (Random House, New York, 1996).
: ESC, you're too modest. This is more of your post from 2000: "It's also used to address a shy child. I think its origin lies in the way of outdoor cats dragging little captives, chipmunks and such, into the house."
: Here's a different comment from the archive: "The most surprising thing about "cat got your tongue" may be its relatively recent vintage. While it certainly sounds as if it must have been dreamt up back in the Middle Ages, the earliest written example listed in the Oxford English Dictionary is from 1911."
: And a third, which appears to be a troll: "The expression "cat got your Tongue" comes from the English sailing ship days, and refers to the cat of nine tails, if the captain or other officer told someone something in secrecy he would 'get the cat' if he was to tell the others, naturally if the others wanted to know what had been said they would ask, tell us, or are you afraid!!! ..I.e. has the cat got your tongue!"
: Troll or not, this last is definitely what another site,
: terms a "CANOE": Conspiracy to Attribute Nautical Origins to Everything, [a] term coined ... on this board to indicate the penchant of some to find an origin in maritime tradition for just about any word or phrase."