We know that lalafells do possess their own language on their home islands, further south of Eorzea; this is evidently where the sounds used in lalafell (and even on the First, dwarven) names come from (and these are, from a real-world perspective, sourced from the syllabary of Japanese). Likewise, roegadyn names are sourced from the language spoken in Aerslaent, far to the north of Eorzea.