Long Dau (ロンダウ Rondau?) is a dead language in Tales of Xillia, having once served as the court language of Long Dau nobility. Only a select elite are allowed to learn the language, and it is Wingul's native language. Upon undergoing the transformation of his booster, he speaks it fluently. Gaius knows Long Dau from Wingul teaching it to him, and Rowen J. Ilbert acknowledges that he studied it when he was young. Other than these three, there are no other known speakers of the language.
The original incarnation of the Long Dau language is Melnics in Tales of Eternia. Like Melnics, Long Dau is heavily based on the English language, replacing phonemes in order to create a new sound. It is an oral language with no writing system, and only a single dictionary is known to exist, written out phonetically in the Rieze Maxian language. Certain exceptions apply to Long Dau's phoneme substitution, such as names and Elympion terms, as Long Dau is restricted to the world of Rieze Maxia. Its sentence structure is designed to remain as simple as possible, with the meaning of the translation holding more important than the English rendition, for example. Without this rule, sentences could potentially be long and convoluted, and it is also for this reason why the language's vocabulary is intentionally simple, avoiding synonyms and other unnecessary variants.