Irish Whiskey was a type of alcoholic drink native to Ireland on Earth.
Dermot Cusack and Christopher Pike consumed some Irish Whiskey whilst they went over personnel files, selecting the crew for Pike's new command, the USS Enterprise. (EV comic: "Flesh of My Flesh")
In 2373, Keiko O'Brien (who was inhabited by a pah-wraith at the time) gave Miles O'Brien a neat single malt Irish whiskey during his birthday party. (DS9 episode: "The Assignment")