This article is about a hypothetical ancient natlang family. For the languages of water elementals in fantasy settings, see Elemental languages.
The Aquan languages are a hypothetical European language family proposed by Jörg Rhiemeier. The languages are all extinct and unattested, leaving only traces in other languages, mainly in form of the Old European hydronymy and substratum loanwords in the Indo-European languages of Central and Western Europe. The name "Aquan" is derived from Latin aqua 'water', a word that is limited to the westernmost branches of Indo-European (Italic, Celtic and Germanic) and also occurs in the Old European hydronymy, and may have been the Aquan common term for a watercourse.
According to Rhiemeier, the Aquan languages were spoken in Late Neolithic to Copper Age Central and Western Europe and form a branch of the Indo-European family that separated from the rest of the family at an early date. (He calls this larger version of the Indo-European family "Macro-Indo-European".) He formerly assumed that Proto-Aquan may have been spoken around 5500 BC by the people whose archaeological remains are known as the Linear Pottery culture; see Europic for this obsolete hypothesis. These people, however, were genetically not very close to the Yamnaya people of Copper Age Ukraine and southern Russia who are widely identified with Proto-Indo-European; hence, he now considers this connection doubtful, instead proposing that Proto-Aquan resulted from the first wave of "Kurgan" expansions which would have brought the language to Central Europe ca. 4500 BC. From there, the languages were carried north, south and west by various daughter cultures. The last holdout of Aquan languages may have been in the British Isles, where these languages may have been the substratum responsible for the "un-Indo-European" appearance of the Insular Celtic languages.
The Aquan languages seem to preserve some archaic features of an early stage of Proto-Indo-European, such as a three-vowel system (*/a i u/) without ablaut, and a more agglutinating morphology. Substratal evidence from the Insular Celtic languages may indicate that the insular branch, at least, may have been head-initial and active/stative, with a tendency to phonologically run together syntactically closely associated words (such as noun and adjective within a noun phrase).