Originally set to the tune of the Ancient melody "The Londonderry Air," this song has been rumored to have been written about a father singing to his son, who apparently was named Danny. The song was based on a story about an Irish father whose son was eventually going off to war in Ireland.
Many of the traditional versions have only 4 verses, but the most recognized version, and the most common one for Ireland, has six verses in total. (thanks, Annabelle - Eugene, OR, for above 2)
Some of the many artists who recorded this include Judy Garland, Bing Crosby, Johnny Cash, Patti LaBelle, Glen Miller and Elvis Presley.
Tradition links the composition of the piece to a seventeenth century blind harpist, Rory Dall O'Cahan. In 1851, Jane Ross, of Limavady, Co Londonderry, wrote down the music after hearing it played by an itinerant fiddler. The "Londonderry Air" became popular with the Irish diaspora, especially in America, and in 1910, Frederick Edward Weatherly, an English lawyer, who is thought never to have set foot in Ireland, wrote the words.
According to the book Sunshine and in Shadow: The Family Story of Danny Boy written by Weatherly's great grandson Anthony Mann, after Weatherly penned the lyrics, he struggled to find the right melody for the song. Eventually Weatherly's sister-in-law, Margaret Enright, an Irish American known as Jess, introduced the tune he was looking for when she sung "Londonderry Air" to the lyricist while visiting his home in 1912. Weatherly shaped the lyrics to the tune and published "Danny Boy" soon after. However, Frederic never acknowledged Jess's contribution, which caused a major division in the family. Mann explained to The Irish Times: "Jess, who resented for the rest of her life the fact that Fred had taken this melody and made it his own, went on (with Eddie) to die in poverty while Fred enjoyed both fame and wealth."
Prudish Victorians, concerned that "Londonderry Air" bore too close a resemblance to the phrase "London derrière," preferred to refer to it by the title "An Air From County Derry."
If you don't like this song or are just sick of it, you're not the only one. When we asked Matt Kelly of the Dropkick Murphys
about his favorite Irish songs, he replied: "I love 'Come Out Ye Black and Tans,' 'At The Rising of the Moon' is a great tune, and 'My Brother Sylveste' is a great song. Those are some of the bigger ones. You know, if I never heard 'Oh, Danny Boy' or 'Smile Again,' it would be just fine."