Basically, there are so many languages in d&d role-playing game. From those languages this Bavanese 5e language was spoken by may Bavanese people of the kingdom of Bawa, of an island kingdoms of the kara-tur. Normally, it proper name is unknown and it has no details to know more about it. Actually, it might be a same language like the Bawani and/or Bertanese.
“Kara-Tur: Here the ancestor feats and also the martial arts styles” in the dragon #315 notes that it would be used names from the languages of Philipines or from the indonesia. Here the ronin challenge bases the lidahan on the Indonesian, which is suggesting the possible, hypothetical connection in between them.
Attributes Of Bavanese 5E Language
Language Family: Kara-Turan languages
Spoken in: Bawa
Spoken by: Bavanese
Based on: Indonesian or Filipino