Quick summary: excavations from the Boğazköy-Hattusha archaeological site (present-day Turkey) unearthed a tablet. That tablet is written mostly in Hittite, but it mentions an idiom from another language, “of the land of Kalašma”, that would be spoken in the northwest of the Hittite empire (also in what’s today Turkey).

Said language would be an Anatolian language; so it’s a close-ish relative to Hittite (and Luwian, Palaic, etc.), and ultimately related to Russian, English, Italian, Hindi etc. (it’s all Indo-European).

EDIT: @chemical_cutthroat@lemmy.world linked an even better source. Enjoy!