Sure, celebrating St. Paddy’s Day by partying is an American invention, but so is an important element of this traditional Irish outlaw ballad. The song was popularized by a Clancy Brothers recording released in 1961 (this video is from 1963) and can be traced to broadsides published in the 1860s, though it tells of events of a half-century earlier. In the early Irish versions, the brave and undaunted Brennan is betrayed by a man. In American versions published soon after, his betrayer becomes a “false-hearted woman.”
Why do the Clancys sing the American version? Like many folk songs, “Brennan on the Moor” was saved from extinction by traveling folk-song collectors, but it was saved from obscurity by Burl Ives, who recorded it in 1949 for his LP “Wayfaring Stranger.” The original broadside ran to 12 stanzas. Ives trimmed it to five, but also added a new final verse that never appeared in any of the scores of known variants; in the album’s liner notes, Ives attributed it to author and screenwriter MacKinlay Kantor. Late in their career the Clancy Brothers began using the extra stanza as well.
Hardcore Dylan fans might recognize the melody, which Dylan repurposed for a song he called “Ramblin’ Gamblin’ Willie.” Dylan recorded it in 1962, but it was available only on bootlegs until 1991.