The penny whistle is one of only two instruments ever invented in England. At the time (late 18th C, IIRC) wooden whistles were common, and there was a particular farmer who played the whistle and kept it in his back pocket. Unforunately he kept sitting on it and breaking it, so one day he had the bright idea to go to his local smithy and have one cast out of tin. After a bit of hard work by the smithy, the whistle worked properly and didn't break. A few years later, the farmer in question was made homeless (I'm not entirely sure why). Anyway, he wen't to the smithy, had himself cast as many tin whistles as he could fit in his cart/wheelbarrow/whatever, and went travelling the countries and selling them for a penny each. Mostly, he sold them to workers from Ireland helping build roads (and later railroads+canals) across the UK. They were then taken back by the Irish to Ireland, where they gradually grew more popular.