There’s one song on an album I’ve edited with an “Adaption of lyrics by” credit. The original work is not in MB as it was written in the 13th century and the original music is unknown.
The lyricist is Francesco d’Assisi and the adapted work is “Canticle of the Sun”. It was re-used for song lyrics several times. Some do not credit a lyricist, some works have d’Assisi as lyricist and a translator named, but in case of my edit, there’s none.
It’s not related to the various “Brother Sun/Sister Moon” versions which all have different lyricists (incl. Donovan).
It’s relatively close to the translation given on Wikipedia:
“Adaption” most probably means adding or skipping words for a more fluid verse. I could add a translator [unknown], but this wouldn’t cover the adaption done.
EDIT: I struggle even if I have the original work (I created it in test.musicbrainz). I only managed to say it’s a “translated version of” the work, but that’s not true.