Maybe this was answered before, but I couldn't find anything, what is Phusis, has it been mentioned anywhere else?

When the thing-called-Serwe is chasing the Survivor's son, quote from the latter's perspective:

The thing commanded Phusis - there could be no question

(The Great Ordeal, UK)

More interesting stuff, Gilcunya is described as the holy tongue of the nonmen quya and is a debased version of Auja-Gilcunni, the base language of Cunuroi - seperate again from Ihrimsu, which the nonmen of Ishterebinth speak. 

Culturally, this suggests different languages between mansions.

Apologies if this has been brought up earlier (and for taking the discussion back to much earlier in the thread!), but I thought this made sense, the Quya using a different language for their sorcery (which I presume is what 'holy' implies?), and not Ihrimsu which a common tongue...

“Vulgar languages, especially when native, stand too close to the press of life. Their meanings are too easily warped by our insights and experiences. The sheer other-ness of Gilcûnya serves to insulate the semantics of sorcery from the inconstancies of our lives.

Bakker, R. Scott (2010-05-06). The Thousandfold Thought (Prince of Nothing) (Kindle Locations 3415-3417). Orbit. Kindle Edition.

and

Gilcûnya—The tongue of the Nonmen Quya and the Gnostic Schools, thought to be a debased version of Auja-Gilcûnni, the so-called “ground” (or first) tongue of the Cûnuroi.

Bakker, R. Scott (2010-05-06). The Thousandfold Thought (Prince of Nothing) (Kindle Locations 9844-9845). Orbit. Kindle Edition.

Which may mean that the Quya use Gilcunya to preserve the meaning of their sorcery, just like the Mandate, but doesn't mean much to Nonman society in general because it is a derivative of an already ancient and not commonly used tongue, Auja-Gilcûnni?

Ihrimsu, the glossary says, is the tongue of Injor-Niyas (=Ishterebinth?), the last Nonmen nation - which, as Curethan says, might suggest different languages in different mansions.