This article concerns content exclusive to Warcraft RPG and thus unlikely to be canon.
Aquan is a language of the water elementals of the Abyssal Maw. It is also known by conglomerates with the sub-type of water. Perhaps a dialect of Kalimag.
This article or section includes speculation, observations or opinions possibly supported by lore or by Blizzard officials.*
"Aquan" has an apparent connection to DnD derived generic languages, which apparently can be found in DnD rule books.