The Basque carol, "Birjina gaztettobat zegoen", is believed to be from the 18th century, and was collected by Charles Borde in the volume Douze Noëls populaires of the series Archives de la tradition basque (1895). It is reproduced (with harmony provided by the authors) in The New Oxford Book of Carols, by Hugh Keyte and Andrew Parrott. They also provide Baring Gould's version, with music arranged by [C.] Edgar Pettman. The song was published in 1922 in Baring Gould and Pettman's The University Carol Book, so both the translated/paraphrased text and arrangement are public domain. The copyright Jim Dixon cited above applies to the hymnal he quoted from, not to the song itself, except perhaps to the extent John Wickham modified the Pettman arrangement.

The Hymns and Carols of Christmas site asserts that the Basque text was based upon the Latin song "Angelus ad virginem", from the 13th or 14th c. They also give an alternative for the third line of the fourth verse: "And everyone throughout the world forever saved".