Some fun etymological connections around the PIE root (s)teg
Jad is a thatcher. Aside from the obvious semantic relationship thatching has to covering, it’s also a descendant of the PIE root (s)teg, meaning “to cover.” Stephenson’s creation “the Teglon,” a game of covering a board with tiles, has a straightforward connection to the Latin tegula, meaning “tile,” and is also a descendant of the PIE root (s)teg.
Anathem’s Mathic-related coinages and names are almost all derived from Greek or Latin (“Jad” being the sole exception, as far as I can tell). Generally speaking, Anathem uses Greek roots to represent an older, purer thing, and Latin to represent a newer and possibly tainted thing. For example, anathem is a merge of both anthem and anathema. Anthem is from the Greek antiphon, meaning “a sung response.” Anathema, meaning “accursed,” is derived from the identical Latin word, but derives from a Greek word meaning “a thing devoted,” literally “a thing set up (to the gods).”1
So going back to the Teglon, the Latin root is clear, but there’s also a viable Geeek root: στέγω (stégō), “to cover closely, so as to keep water either in or out.” This is thematically related to how Incanter-style Third Sack praxis works and manipulates the Hylaean Flow. Think about what Jad says when he destroys the wireless transmitter while en route to the Daban Urnud:
Jad said, "The leakage was forcing choices, the making of which in no way improved matters."
(part 11, ADVENT, Causal Domain)
There are quite a few references to water/flowing in the novel that provide metaphors for the Hylaean Flow.
Hence the cleverness of the book’s title, that the same thing is both what’s offered up/sent out, and the response. This is relevant in the climax, when, during the Third Sack, the Arbrans sent out a prayer for help to higher powers, and are eventually answered by the Urnudans, who themselves see the Arbrans as the higher power. (It helps if you squint a little bit.)