Hello! We are six students of English Studies from University of Seville, and this is a project of New Technologies Applied to English Language.

DON'T HAVE A COW

Meaning: Calm down!; Don't get so excited!
It's origin is probably from the UK from the late 1950's. It's also used as a catch phrase on some of the Simpson shows.
The phrase used prior to Don't have a cow was Don't have kittens, meaning the same thing.
Example:  (The Simpsons.) Chill out, man! Don't have a cow! Aw, don't have a cow, Dad!



BUY PIG IN A POKE
Meaning:  to buy something without looking inside first.
It’s originating in the Late Middle Ages, when meat was scarce, but cats and dogs (puppies) were not. The scheme entailed the sale of a suckling pig in a poke (bag). The bag would actually contain a cat or dog (substantially less valuable as a source of meat), which was sold to the victim in an unopened bag. The French idiom acheter (un) chat en poche (to buy a cat in a bag) refers to an actual sale of this nature, as do many European equivalents, while the English expression refers to the appearance of the trick.
Example: If you don't get a good look at the engine of a used car before you buy it, you'll wind up buying a pig in a poke.





FREE AS A BIRD
Meaning: completely free to do what you want and without any worries.
This idiom is related to the freedom of the birds, because they are not tied and they can go wherever they want, they are animals that live in freedom.
Example:  She'd been travelling alone around the world for a year - free as a bird.