To coin a phrase

We've all heard the phrase 'to coin a phrase', but what does it actually mean?

'To coin a phrase' is actually an idiom, or expression used to describe the creation of a new figure of speech. The person who first used this expression or description is the one who coined it.
While this was the original defintion of the phrase it is now rarely used in this way, and is instead used ironically before a cliched or overused staement, meaning instead 'as one might say'. Used in this way its purpose is to draw attention to the cliche, or even as an admission that you know it is a cliche and you're using it anyway.

While there is no record of the person that coined the phrase 'to coin a phrase',  the earliest use of it is from an american newspaper in 1848, it has been widely used sinse the mid 20th century. The name comes from the method of creating coins, during which they are 'coined', or created by stamping the metal with a die. The word coin itself was originally derived fron the early 14th century meaning of coin, which meant wedge, and was used to describe the wedge shaped dies used in the creation of money. The metal blanks which were 'coined' by the dies later took their name.

The phrase later became associated with language, and the coining of words was used to refer to linguistic inventions. Spakespeare referred to the coining of language in Coriolanus

"So shall my Lungs Coine words till their decay."  

Interestingly, while most phrases come into popular usage by chance, there are still people who actively try and get phrases coined, as in this blog: http://coinaphrase.blogspot.com/