Pseudotranslation is the idea—prevalent in, but not unique to, SF/F—that the author did not write the stories we read, but translated them from some fictional language into English (or whatever other language we happen to be reading in).
In other words, my brain is interpreting anathem not as a word in a made-up language—even though I am told explicitly that that is what it is!—but as an English translation of such a word, in the same way that every other word in the novel is an English translation. The fiction holds together because I’m never asked to imagine what that original made-up word might look like.
It follows that problems sometimes arise when I am asked to do that… Why are these words untranslated when every other word is not?
Their approach is to indicate the difference to the reader stylistically (e.g. italics, inside chevrons <>) rather than making up a word wholesale, and if necessary making up an English word or phrase that theoretically represents the foreign concept.