Easternese is the language spoken in Tai-tastigon and—given it's name—likely commonly spoken elsewhere in the Eastern Lands. If that is the case, it likely came to be such by being the language of the Old Empire. It is related enough to Southron that Jame, who speaks Easternese, can understand some Southron words from their resemblance to Easternese cognates, but is still distant enough that Jame can barely understand the soldiers who accost her in Hurlen.