The Lingua Incognita was a "secret language" used in the Dawudid Empire . Its primary use was for communications of importance among high families, and as a consequence, was only taught to a very few select families who were considered trustworthy enough to teach and learn it; the Froylán-Salazar clan, which also produced a number of mentats were considered to be the most prominent of those who could speak it. The Emperor Ghufran, instituted the death penalty for those who taught or learned the language without a legal writ which stated that the individual had the right to do so.
The Lingua Incognita was devised by the first Emperor, Dawudid I, and was used to keep notes on the battlefield. was reported to be an incredibly difficult language to master, due to its high grammatical complexity.