What it means: This is used when someone is rendered speechless. Where it comes from: There are two legends as to where this phrase comes from, and none of them are particularly nice. The first one is that whenever someone was convicted of a crime, their punishment was to have their tongues cut out. This obviously made it difficult for them to speak (if they could) and sometimes the people who executed this punishment would enjoy a giggle by feeding the person's tongue to the cats, and then make them watch the cat eat it. The second is that the English navy would punish sailors by flogging them with a whip called the cat-o'-nine-tails. Sailors were whipped to the point where they were left speechless or unconscious.
