The "Who Let The Cat Out Of The Bag?" Story

It was an ordinary day.  Watching my favorite Philadelphia Eagles play on television while enjoying a dish of tapioca pudding for dessert.  After eating my dessert I grabbed my new laptop and began writing about idioms.  Know what an idiom might be?   If not, I can tell you that it is a group of words established by usage as having a meaning not deducible from those of the individual words.  Such as...kill two birds with one stone which really doesn't mean to actually kill two birds, but to get two things done with one act.  Another would be...under the weather, which means you don't feel well.  Lost yet?  So, where do we get these phrases and how do we use them in the English language?  Well, there is one phrase that both Carol and I use quite a bit which is, "let the cat out of the bag!" Now, we do have two cats, but we have never put them in a bag.  The statement is actually meant to tell someone about a secret or surprise that was just revealed.  It does seem that many idioms have to do with animals with another idiom being "straight from the horse's mouth!"  So why do we use idioms?  Seems that these expressions use words in a non-literal way to mean something other than the actual meaning of the individual words and they're often quirky, funny or perplexing such as "spill the beans" or "break a leg."  As far as "letting the cat out of the bag", it was first used in a 1760 book review in the London Magazine when the reviewer complained that he "wished that the author had not let the cat out of the bag, " presumably referring to some kind of plot point.  Why did they say what they did?  Was there an actual meaning they had in mind?  As I continued to read about idioms I did find that at one time shady livestock vendors in marketplaces would try and swindle their buyers.  If someone would buy a pig the vendor would sneak a cat into the bag instead, cheating the buyer out of the higher price for a pig.  When the buyer arrived home and actually left the cat out of the bag, they would realize they'd been scammed, hence the phrase's associate with revealing a secret.  Now, it does mean something slightly different in other languages.  In both Dutch and German it means "to give a cat for a hare" which translates to actually "buying a cat in a bag."  And how about the idiom "a pig in a poke."  That dates back to the 16th century and refers to making a deal or purchasing something without fully validating it.  And, how about..."knocking on wood."  Does that mean knock on a wooden door?  One final explanation for letting the cat out of the bag has to do with the "cat o' nine tails" which is a whip made with nine intertwined cords that was used as a form of punishment in the British Royal Navy and in prisons until the 1840s.   In this case it was called a "cat" since the marks it left behind looked like cat's scratches.  And, just how would someone get a cat into a bag in the first place?  We have two cats and to get them in a bag would be next to impossible to do.  So, saying "let the cat out of the bag" doesn't really mean anything, since I just can't see anyone getting a cat in the bag in the first place...idiom or not!  It was another extraordinary day in the life of an ordinary guy.