Adynaton (ad-in-aah-ton)

It just means “impossible”.

The idea is that you say “NO" or "NEVER" in a flowery way.

The Labour Party will win an election when pigs fly...

Not everything impossible is an adynaton. 

For example Peterborough United winning the cup is not an adynaton because it is a stand alone. But Caroline Lucas becoming Prime Minister is about as likely as Peterborough United winning the cup is.

In the first we just get a statement of the impossible. In the second, we actually use the impossible idea to prove that something will never happen.

And adynatons are fun to do.

“The Titanic will never sink”, said Captain Smith, “until all the icebergs in Arctic waters have melted.” (He didn't really say this: I made this one up.)

If you want to tell someone you love them, use an adynaton.

Doubt not that the stars are fire;
Doubt not that the sun doth move;
Doubt truth to be a liar;
But never doubt my love.

Hamlet was telling the wretched Ophelia that he loved her.

Selling stuff?

We will keep on producing delicious chocolate until it goes out of fashion.

Religion:

“Can a woman's tender care / Cease towards the child she bare? / Yes, she may forgetful be,/ Yet will I remember thee.” William Cowper.

WH Auden.

For some reason he is getting fashionable now. He flourished about a century ago.

“I’ll love you, dear, I’ll love you 

Till China and Africa meet, 

And the river jumps over the mountain
 

And the salmon sing in the street,

I’ll love you till the ocean
's folded and hung up to dry

And the seven stars go squawking
Like geese about the sky …”

Adynaton? It will end when English ceases to be the world's premier language.