I heard an explanation that in the past the Irish really like to dance, but either the church or the ruling class (cannot remember which the article stated) decided that it was decadent and sinful, so they banned dancing. People would spy on each other and report anyone who was dancing. They created a dance style that someone spying through a window from a distance would not be able to report that they saw people at a gathering dancing.
Probably not true, but makes a good story.