This opening post will not submit the lyrics set to music by Brahms just yet;
my intention is to frame this Lied, this German art song, before posting the text.

In fact there are two traditions, textually speaking, being woven together by Brahms in order to compose this song.

"Wiegenlied" of course means cradle song, or lullaby.
And no, this is not the well-known Brahms Lullaby,
it is a different song altogether.

To be specific:
Opus 91, no. 2, by Johannes Brahms, is composed for
mezzo-soprano solo voice and piano, with a fiendishly difficult obbligato for solo viola.
NOT violin, which would complement a high soprano voice;
for the deeper, earthier sound of a woman's mezzo-soprano or contralto voice,
Brahms rejected the violin in favor of the viola
which is lower in pitch and richer in tone.

The words initially sung by the solo singer are:
"Die ihr schwebet um diese Palmen in Nacht und Wind,
Ihr heil'gen Engel,
Stillet die Wipfel!
Es schlummert mein Kind."

This is poet Emanuel [von] Geibel's translation of a text,
dated somewhere near the year 1600 AD, attributed to Lope Felix de Vega, and originally
in Spanish:

"Pues andáis en las palmas,
Ángeles santos,
Que se duerme mi niño,
Tened los ramos."
There are a total of three verses and a single chorus which varies slightly in the text at the end of each verse.

Now:
Brahms does not include, in his Geistliches Wiegenlied,
the text for any other lullaby; but if you see the musical score,
you will notice words printed at the beginning that are not used,
and they are directly in the score, under the viola part.

The reason for this, is that
the viola, not only at the opening of the song but
at regular intervals between every verse and at the very end,
is directed, by Brahms, to play
the MUSIC, the melody, of an old German carol ("Altes Lied"):

"Josef, lieber Josef mein,
Hilf mir wieg'n mein Kind'lein fein,
Gott der wird dein Lohner sein,
Im Himmelsreich der Jungfrau Sohn, Maria, Maria."

That is not the entire melody/text, only the beginning, and that
is the only part that Brahms borrows; he does not set the part
that goes
"Eia! Eia!" and continues to the end of the carol lyric,
also very melodic and easy on the ear.

The carol lyric excerpt, as I have submitted it in this post,
is copied exactly from Opus 91, no.2, from the score
by Johannes Brahms.
Again, the solo singer never sings these words,
but the viola player plays the first part of the carol melody.