Poitín is another name for what's essentially Irish moonshine — un-aged liquor made from wheat and rye, boiled in a pot still. The rare auld mountain dew, as it's sometimes know, is the stuff of folklore legend, immortalized in stories and plays and songs like "The Hills of Connemara."
Though you can purchase commercial versions of the stuff today, it's not much different than any white whiskey on the market. But it used to be illegal … sort of. As explained in the wonderfully antiquated video above, people would sneak up into the mountains to distill their poitín (so as not to blow their houses up, or fill them with noxious fumes). The identities of the bootleggers was generally an open secret in the community, but it was still the duty of the Garda (police) to stop them — but only from making it, not from distributing or drinking it. As long as you weren't caught in the act of distilling, they were generally willing to turn a blind eye to whatever else you did with your poitín; sometimes the Garda would even buy a bottle from you.
It's a funny look at prohibition laws, reminiscent of some ways that marijuana decriminalization has been handled more recently.
Image: Ethanbentley / Wikimedia Commons (CC-BY-SA 3.0)