That is Benjamin's offering to the search for the one language underlying all human speech (that search in which Wittgenstein, Heidegger, and Cassirer were simultaneously engaged). It is the language of God. All meaningful speech operates as the trace of that true language, and is thus, so to speak, on the way towards it. We cannot directly say or deduce this in our own languages but it shows itself in certain configurations of the use of language, especially in the translation of works of literature.
p. 101 TIME OF THE MAGICIANS by Wolfram Eilenberger published by Klerr-Cotta, Stuttgart 2018