Where does “Dnieper” come from?

Dnieper is an English name for a major river, from Old East Slavic Дънѣпръ, derived from Proto-Slavic Dъněprъ, whose original meaning is uncertain.

Ancestry of “Dnieper”, step by step

Step	Language	Word	Meaning
1	Russian	Днепр	Dnieper
2	Old East Slavic	Дънѣпръ	—
3	Proto-Slavic	Dъněprъ	—