The words to "Danny Boy" were written by English lawyer and lyricist Frederic Weatherly in 1910. Although the lyrics were originally written for a different tune, Weatherly modified them to fit the "Londonderry Air" in 1913, after his sister-in-law in the U.S. sent him a copy. Ernestine Schumann-Heink made the first recording in 1915. Weatherly gave the song to the vocalist Elsie Griffin, who in turn made it one of the most popular songs in the new century.
Jane Ross of Limavady is credited with collecting the melody, the "Londonderry Air", in the mid-19th century from a local fiddle player.
There are various theories as to the true meaning of "Danny Boy". Some listeners have interpreted the song to be a message from a parent to a son going off to war or leaving as part of the Irish diaspora. The 1918 version of the sheet music included alternative lyrics ("Eily Dear"), with the instructions that "when sung by a man, the words in italic should be used; the song then becomes "Eily Dear", so that "Danny Boy" is only to be sung by a lady". In spite of this, it is unclear whether this was Weatherly's intent, or simply a publisher's note; Weatherly did, however, acknowledge that "Danny Boy" was sung "all over the world by Sinn Feiners and Ulstermen alike", and noted that the song had "nothing of the rebel song in it, and no note of bloodshed".