This is the passage that had me reaching for the bookmark, eager to dive into the novel once I got back home:
He'd become obsessed with the untranslatable: his idea, and the subject of his thesis (or what had been a thesis some years earlier, before it suddenly imploded and went unfinishable on him overnight), was that every language on earth contains at least one crucial concept that cannot be translated.
Not just a word but an idea, like French deja vu: perfect and crystalline in its native language, otherwise explainable only by entire clumsy foreign paragraphs or not at all.
In Uupik, a language spoken by the Inuit along the Bering Sea, there is Ellam Yua: a kind of spiritual debt to the natural world, or a way of moving through the world with some measure of generosity, of grace, or a way of living that acknowledges the soul of another human being, or the soul of a rock or a piece of driftwood; sometimes translates as soul or as God, but meaning neither.
In a Mayan language, K'iche there is Nawal: one's spiritual essence but separate from the self; one's other, not exactly an alter ego or merely an avatar but a protective spirit that cannot be summoned.