Literary Device

Epigram: A very short witty poem usually written as a brief couplet that expresses an idea or remark in a clever and amusing way with a witty or ingenious ending.

Example:

Bruce Bennett, "Ironist"

I mean the opposite of what I say.

You've got it now? No, it's the other way.

This is a clever epigram because the idea of "meaning the opposite of what I say" is expressed in the end or possibly not when the speaker says "No, it's the other way" which could mean that it is not correct or if its the opposite then it correct. Either way the last line of the poem is clever and somewhat confusing.

Function: Epigrams are not really used for any other purpose than to just be amusing and possibly show how clever one is by playing around with the idea of things and mixing them up. Many writers use them in stories or poems to say something but without really saying what is actually meant such as in this poem:

God bless our good and gracious king,

Whose promise none relies on,
Who never said a foolish thing,
Nor ever did a wise one.

At first you think the king is a great person but in the end you realize that he may not be so bright and has never done anything. However you cant actually take that out of the text.