Deh₂nu

Deh₂nu- is a Proto-Indo-European goddess of rivers. Some people think that this is based on the Vedic goddess Dānu, the Irish goddess Danu, the Welsh goddess Don, and the names of some rivers such as the Danube, Don, Dnieper, and Dniester. But, Mallory and Adams say that there is no proof for a specific river goddess in this mythology, only the idea of rivers being important in Indic tradition.
Some people have suggested a sea god named *Trih₂tōn based on the Greek god Triton and the Old Irish word trïath, which means "sea". Mallory and Adams do not think this is true because there is only a small possibility that the words are related, and there is no evidence of a similar god in Irish mythology.
The goddess is also linked to Ossetian Donbettyr, who is said to give "three scones with honey" to those who turn their waterwheels. Donnán of Eigg might be a Christianized version of this deity. 
Some stories say that the goddess fought a hero named H2nert, and her possible descendants include Nart from the Nart saga, Indra, and Njord.
There’s a central Asian river called Dan. Its name might come from Dehnu