Glendalough Double Barrel Irish whiskey is called "double barrel" because it is aged for 3.5 years first in American Oak ex-bourbon casks (very common in the whiskey world typically featuring notes of caramel and vanilla) and then 6 months Spanish sherry casks (common in the scotch whisky world typically featuring a light wine color and aroma). This makes it a younger styled whiskey that tends to signal a celebration of the grain. They call it a "single grain whiskey," though it features a blend of malted barley and corn (wouldn't that be "double grain" or "dual grain"?) and suggests a blended style of whiskey. They suggest looking for flavor notes of butterscotch, honey, and maraschino cherry among others.
Glendalough Distillery was opened as an independent craft distillery to "recapture Ireland's lost heritage of great spirit production." It is named for the beautiful Glendalough Valley, which translates as "the glen of two lakes" and named for a valley in Ireland. The labels feature St. Kevin of the 6th century, who lived in a cave in the valley. Legend has it that he was so still a blackbird nested in his hand. It was founded in 2011 by Donal O'Gallachoir, Brian Fagan, Barry Gallagher, Kevin Keenan, and Gary McLoughlin.