Like most tales from the Emerald Isle, the origin of Irish Coffee seems to have more versions of its history than could possibly be true.
The idea of mixing a spirit or liqueur with coffee most likely has heritage in other parts of Europe. The Viennese seem to have a drink similar, as do the French, but the most widely accepted idea is that a Chef in Limerick. Ireland, post WWII, working in a restaurant at Foynes Port (a flying airplane hangar that was a stop off for fuel) wanted to give his layover folks something to warm up on one of those blustery and chilly nights near the Irish Sea. So he devised a simple drink of strong, black coffee and simply added some sugar, Irish Whiskey (warms hearts and hearths everywhere) and a dollop of cream.
One such passenger, a travel writer for the San Francisco Chronically named Stephen Dalephane was fortunate enough to be warmed by the elixir and when back home in San Francisco, asked a local bartender at the Buena Vista Hotel to try and recreate. He did.
Debate the origin all you want but I think this “poem” says it best:
Cream – Rich as an Irish Brogue
Coffee – Strong as a Friendly Hand
Sugar – Sweet as the tongue of a Rogue
Whiskey – Smooth as the Wit of the Land
2 oz Irish Whiskey
1 t sugar (brown is best)
Fresh black coffee
2 oz heavy cream, poured over back of spoon to float