Wee Bairns was a brand of alcoholic beverage, an Earth-style scotch whisky. This drink was a favorite of Irishman Miles O'Brien. The Wee Bairns bottle is labeled with an image of a starship engine room.
In the year 2373, O'Brien received a bottle of Wee Bairns from Jadzia Dax for his 45th birthday. (DS9 episode: "The Assignment")
Mister O'Brien shared a bottle of Wee Bairns with his friends in Benjamin Sisko's quarters during a dinner party. (DS9 episode: "In the Cards")
In 2375, O'Brien used the replicator to create a chewing gum infused with the flavor of Wee Bairns scotch. He offered a stick to Julian Bashir. (DS9 episode: "Take Me Out to the Holosuite")
In Star Trek Discovery, Captain Lorca is seen sharing a bottle of Wee Bairns with Admiral Cornwell (S01E06 "Lethe" - BC-S).