Danube
"Danube" is an Old European river name derived from a Proto-Indo-European "*dānu". Other river names from the same root include the Dunaj, Dzvina/Daugava, Don, Donets, Dnieper, Dniestr, Dysna, Tana and Tuoni. In Rigvedic Sanskrit, "dānu" means "fluid, drop", in Avestan, the same word means "river". In the Rigveda, "Dānu" once appears as the mother of Vrtra, "a dragon blocking the course of the rivers." The Finnish word for Danube is Tonava, which is most likely derived from the word for the river in Swedish and German, "Donau". Its Sámi name "Deatnu" means "Great River". It is possible that "dānu" in Scythian as in Avestan was a generic word for "river": "Dnieper" and "Dniestr", from "Danapris" and "Danastius", are presumed to continue Scythian "*dānu apara" "far river" and "*dānu nazdya-" "near river", respectively.
Hydronym
Hydronyms from various languages may all share a common etymology. For example, the Danube, Don, Dniester, Dnieper, and Donets rivers all contain the Scythian name for "river" (cf. , "river, water" in modern Ossetic). A similar suggestion is that the Yarden, Yarkon, and Yarmouk (and possibly, with distortion, Yabbok and/or Arnon) rivers in the Israel/Jordan area contain the Egyptian word for river ("itrw", transliterated in the Bible as "ye'or").