Like other Lutheran chorales, this one is based on a Latin chant: The Magnificat Antiphone "Veni Sancte Spiritus" that you can find on p. 307 of the Antiphonale Monasticum (Solesmes 2005). The Cantus database lists 109 concordances. The full text of the antiphone is

Veni sancte spiritus reple tuorum corda fidelium et tui amoris in eis ignem accende qui per diversitatem linguarum cunctarum gentes in unitatem fidei congregasti alleluia alleluia

Unlike other Luther chorales like "Nun komm der Heiden Heiland" (based on "Veni redemptor gentium"), it is not based on the medieval chant melody and uses a different meter, which makes it impossible to use the original text with a polyphonic setting of Luther's chorale. In this case, neither the translation of the antiphone nor the melody are by Luther: He only added two further stanzas. Melody and text of the first stanza predate Luther and are from 1480 (at the latest).

If you are looking for a Pentecostal chorale by Luther that can be sung with the original Latin text, have a look at "Komm Gott Schöpfer Heilger Geist" that is based on "Veni creator spiritus" and even has the same meter. There is a homophonic setting by Sethus Calvisius and elaborate motet-like settings by Balthasar Resinarius and Johann Eccard. If your hymnal for the congregation includes this chorale, you could, e.g., sing the Latin version by the choir alternatim with the congregation, who thereby, as a collateral benefit, understands what the choir is singing.

Has anyone done a concordance of Lutheran chorales that were originally entirely Latin-texted?

I found a Latin metric concordance of the choral "Nun ruhen alle walden", which is one of my favorites. The first two of its nine stanzas are:

Quiescunt silvae cunctae,
Et pecudes adiunctae,
Cum vici, tum urbium;
Sed vigila, mi anime,
Et laude prompta maxime
Lauda Creatorem omnium.

Sol abiit recessit,
Sed lumen mihi crescit,
Iesus, lux mentium;
Is splendor orbis terris
E tenebris ac guerris
Adducit ad palatium

Gemini explains:
This translation is historically attributed to Johann Leonhard Frisch (or included in collections of sacred hymns translated into Latin in the 17th and 18th centuries, a time when the use of academic and liturgical Latin was still very much alive in Lutheran circles for didactic or choral purposes). The translation attempts to retain the original rhythmic structure (the same as the hymn Innsbruck, ich muss dich lassen ), thus allowing the Latin text to be sung to exactly the same melody as the four-part German chorale harmonized by composers such as Johann Sebastian Bach.

Liturgical Use: In educated Protestant communities of past centuries, it was not uncommon for school or academic choirs to sing Latin versions of German chorales to keep alive the practice of the Latin language."