"Etymology
Irony is believed to have been imported to English from the Latin ironia in 1502, in turn from the Greek eironeia, a conjugation of eiron - to dissemble, such as lying by omission or by concealment of true intent. During the word's Latin use, the lie by omission was dropped from its meaning; ironia is simply lying by concealment of true intent (some group these two actions under the term affected ignorance.) On conversion to english, this definition has been expanded to include not only lies, but some jokes of subtlety.
It is important to bear this history in mind when one attempts to nail down what irony is, as it clears up why the word means specifically things phrased to bury connotation behind denotation. Irony has nothing to do with something coming back to haunt one; it's about doubletalk, two-faced speech and the sly underpinnings of sarcasm and trickery through misphrased honesty."