In Children of Dune Leto II and Ghanima sometimes use an "ancient language" to converse with each other, a language that only they know of:
Leto reverted to the ancient language they used for privacy: "L'ii ani howr samis sm'kwi owr samit sut."
That was where the decision lodged itself in their awareness. Literally: We will accompany each other into deathliness, though only one may return to report it.
The Golden Path is also referred to as "Secher Nbiw" in this ancient language:
[…] words uttered in the ancient language shared only by the two of them in all this universe. Secher Nbiw. If she heard those words: Golden Path […]
In this reddit thread a user claims that it's a attempt to represent Ancient Egyptian, and there's mention of a Wikipedia article that 'confirms' it but that must have been deleted or moved because I can't find it anywhere.
The Dune Wiki also says it's Ancient Egyptian but provides no sources:
The Golden Path ("Secher Nbiw" in the ancient Egyptian language)…
Is the reddit thread and the Wiki correct? Is there anything (textual clues from the novels, notes from Frank Herbert) that proves the language is indeed Ancient Egyptian? And if not, what exactly is this ancient language?