We do not understand speech, because speech does not understand itself, nor wish to; the true Sanskrit* would speak in order to speak, because speech is its delight and essence.
This line is from Novalis' The Novices of Sais, newly reprinted in a translation by Ralph Manheim. (Thanks to Conrad and Forrest, for pointing it out to me.) It strikes me as so similar to Fritz' speech to Karoline about Language, that I think Fitzgerald must have used it as source material. (It is also, I think, quintessentially stoner.)
Another great line from The Novices of Sais, from the chapter titled "Nature":
It must have been a long time before men thought of giving a common name to the manifold objects of their senses, and of placing themselves in opposition to them.
It suddenly occurs to me that "manifold" might be a good translation of vielgestaltete in the first paragraph of Hymns to Night.
*This word is kind of bugging me, because when I read it I see the name of a language, not a type of philosophy. My suspicion is that Novalis intends it to mean "mystic", so I am making that substitution when I read.