This phrase has an intriguing backstory. The English Navy used to lash errant sailors with a whip with many endpoints in the 18th century. This whip was dubbed "the cat" because it frequently had nine endings. So, after a thrashing, when the unfortunate sailor is sulking in a corner or not speaking, other sailors will approach him and mock, "Did the cat catch your tongue?" referring to the whip. This was eventually condensed to Cat got your tongue? Source: http://www.theidioms.com/
