h₂ep-es-
“river, flowing water”Avon, Punjab, affluent
Abstract from *h₂ep- yielding Celtic *abonā > Avon, Latin affluēns > affluent.
Discussion
The PIE form *h₂ep-es- (river, flowing water) is a nominal derivative of the root *h₂ep- (water, river), built with the neuter s-stem suffix *-es- that appears in several of PIE's most archaic nouns. The root gave one of the most geographically widespread cognate sets in Indo-European: the word for river, preserved in hydronyms across a vast territory from the British Isles to South Asia.
The most striking evidence comes from river names. The Avon in England (from Brythonic Celtic *abon-, "river"), the Abhann in Scottish Gaelic ("river"), and the cognate Welsh afon ("river") all continue *h₂ep- in the Celtic branch. The Punjab in South Asia (from Sanskrit pañca-āp, "five waters/rivers") preserves the Indo-Iranian reflex. The Hittite ḫāpa- ("river") provides crucial Anatolian attestation, with the laryngeal *h₂ preserved as the Hittite ḫ — key evidence for the laryngeal theory.
The Latin reflex amnis ("river, stream") is sometimes connected to this root through a different morphological derivation, though the details are debated. More securely, the ancient Celtic tribal name Abrincatui and various Gaulish place names containing abr-/abr- (water) continue the root in Continental Celtic.
The s-stem formation *h₂ep-es- specifically appears in Vedic Sanskrit ápas ("waters, cosmic waters"), a neuter plural that appears in Rigvedic hymns describing the primordial waters from which the universe emerged. The cosmological significance of water in Vedic thought — apas as both physical river-water and metaphysical origin-water — gives this particular root reconstruction a cultural dimension beyond mere vocabulary.
Old Persian āp ("water") and the Avestan cognate āp provide the Iranian parallels. The Ossetian don ("water, river") has replaced the inherited reflex in that language, but the root survives in Iranian toponyms. Tocharian A āp and Tocharian B āp ("water, river") confirm the eastern IE attestation.
The root *h₂ep- should not be confused with *h₂ekʷ- ("water" — the source of Latin aqua) or *wódr̥ ("water" — the source of English water). PIE appears to have maintained at least three distinct water-words, each with a different semantic nuance: *h₂ep- emphasised flowing water (rivers), *h₂ekʷ- may have denoted still or potable water, and *wódr̥ was perhaps the most generic term. The coexistence of these synonyms in the reconstructed lexicon tells us something about the PIE environment: these were people who lived near water, depended on it, and distinguished its forms with precision.