Shidi

As seen in

"Shidi isn't a language you'll find easy for you to speak. I'm not saying you're an idiot or anything, but you're not creature of the flames. Shidi is a language I've only heard in the court of the Efreeti, and even then it was seldom spoken by the common Efreeti. It was mostly spoken by the Sultan and the nobles. When I asked about it my guide was telling me that it was a language that only the Efreeti were allowed to speak and would say nothing more on it while in court.
After court ended I was able to persuade my guide after some coin and a lot of alcohol. Eventually they revealed to me that Shidi was a language that was created by the Sultans father during his time as a slave to a Titan in the past. The Titan was able to understand all the languages and after some experimentation the Sultan's father was able to create a language that the creature couldn't understand. The guide said it was a combination of multiple languages into one that never shared similar structure.
All the Efreeti started to learn this language so planning could be done under the Titans nose. Eventually the Efreeti rebelled against their oppressor. The bloody conflict ended with the banishment of the Titan for just enough time for the Efreeti to escape. After the successful escape to the plane of fire. The Efreeti established their own settlements and started to live among the natives. The first interactions were in Shidi and caused the other races to start to learn that language as well.
After some conflicts with the natives the Sultan's father ordered no Efreeti is allowed to speak such a language except in royal court. It became more stringent as the lower Efreeti started to betray the Sultan and his court in attempts to get into power."
~ Unknown Magi