There are injunctions in the Torah against using the name of God, including one in the Ten Commandments (Exodus 20:7). The name, which occurs in written form throughout the Torah, is not pronounced when reading the text out loud; indeed, it is not currently known how to pronounce it. In most English translations the name is given as "the Lord", which is a translation of the Hebrew word that is substituted for the name when read aloud.
This makes sense as a manifestation of the Outsider, especially in association with an exodus! If the principal narrator of Short Sun indeed communicated with Quadrifons, this would echo Moses, who spoke to God face to face.
Aside: I myself tend to view these correspondences as associational rather than allegorical. Wolfe doesn't have to write the Bible--it's already written. We spend a lot of time here trying to make all the puzzle pieces fit together, but I'm not sure they're meant to. SIlk/Horn might still have Mosaic coloration, even if he wasn't denied entrance to Blue by the Outsider, and even if he didn't have a brother as high priest...hmm... Quetzal as Aaron? Naah.
-- Dan Rabin
*This is WHORL, for discussion of Gene Wolfe's Book of the Long Sun.