ὕδωρ

ὕδωρ (hydor, "HÜ-dor") is water, and it is nearly everywhere in the record: 1,574 occurrences across 126 works. The distribution runs through history, cosmology, and scripture at once — Herodotus's Histories (116), Plato's Timaeus (73), Diogenes Laertius's Lives of Eminent Philosophers (61), Plotinus's Enneads (60), Genesis (59), and the Odyssey (59). Water is what the historian measures, what the philosopher makes the world of, and what the first chapter of Genesis places at the beginning.

The lexica keep it plain and physical. LSJ (Liddell–Scott–Jones, 1940) gives "water, of any kind," and for the sea records the phrase ἁλμυρὸν ὕδωρ (halmyron hydor, "salt water") — as if fresh water were the default and the sea the qualified case. Beekes (Etymological Dictionary of Greek, Brill 2010) glosses it simply "water" and records the Mycenaean form already on the tablets, u-do-ro, the name of a water-jar. So the word is old enough to name a pot before it names philosophy.

Its etymology is one of the deep shared inheritances of the Indo-European languages, and the record carries pointers for it. In Beekes's view (2010), with Chantraine (Dictionnaire étymologique de la langue grecque, 1968–1980) and Frisk (Griechisches etymologisches Wörterbuch, 1960–1972), ὕδωρ goes back to an archaic r/n-stem, *ud-r / *ud-n-, that alternated its endings — the pattern behind English water and Latin unda ("wave"). Because that alternating stem is so archaic, ὕδωρ is one of the words philologists point to when they want to show how the oldest layer of the language actually behaved.

In the Timaeus the word carries cosmological weight, and among the cited surfaces it also reaches scripture, standing in the record at 1 John 5.8.

If the same word carries a clay jar, a river, and the stuff a philosopher makes the world of, where does water end?