It is the act of dropping the soap while a leprechaun proceeds to run through your legs hitting your test tickles. Which have been painted gold yelling, “there magically delicious ”.
When you affix a bar of Irish Spring soap to the floor of a shower with either a nail or glue and then hide and wait for someone to try to pick it up. When they bend over to retrieve it you jump from the shadows and yell "Irish SPRING!!!!!!" and then proceed to anally rape them.