The language of the Romans. Or not. While other universes show that it is often due to humans called Romans speaking it, there isn't evidence to support that it occurred in Erina. The only thing known about it by the Elementals is that humans really liked using the alphabet and the dead language for scientific words. But anything more than that was destroyed in humanities last stand against the Elementals. For a lost language, Latin sure comes up a lot among all the different human infested inhabited worlds in other universes. Not always from the same group of people. Not always on a planet named Earth or some piece of land that looks awfully like a boot. Yet it persists. So it isn't lost exactly. Go to the right universe and people will still be speaking it and coming up with new words. However, in Erina it's as lost as it could be. Who knows who came up with it. Or why the humans decided to make it the language of science. Perhaps the people who created it were important to academia. Or perhaps they simply thought it sounded cool. That, too, happens a lot in other universes. While none of the books or servers that the Elementals recovered afterwards would reveal the answer to this mystery, they saw how much the humans loved to use it even without being able to speak it fluently. And so at least one person involved said, "This language looks cool and has a neat feel to it, why not use it even if we don't understand it." And so, Latin is the scientific language of the Elementals. Even though they don't really get it. But maybe the humans that found it did it for the exact same reason. Where ever this language was from, it probably was used during the era the humans called B.C.E, though no one really cares about something that happened that long ago. It probably isn't important anyway.