Origins of European rivers' names

[Yetos]

No. Celtic 'briga' = hill
ebro -> bask. 'ibar' = valley

and what about Greek Ebros river? is that from Basquez too?

https://en.wikipedia.org/wiki/Maritsa

The earliest known name of the river is Εύρος (Euros, Alcman, 7th–6th century BC).^[4] Proto-Indo-European *h₁wérus and Ancient Greek εὐρύς meant "wide".^[4] The Proto-Indo-European consonant cluster *-wr- shifted in Thracian to -br-, creating the Thracian name Ebros.^[4] Thereafter, the river began to be known as Ἕβρος (Hébros) in Greek and Hebrus in Latin.^[5] Rather than an origin as 'wide river', an alternative hypothesis is that is borrowed from Thracian ebros meaning 'splasher'.^[6]

 

[Yetos]

Douro is from western Iberian romance for of "of gold". If it is also a Celtic name, then it was borrowed, and called something else first.
See also "de oro" (spanish, "of gold") and especially "de ouro" (portuguese). Drop the first 'e' and combine the two words, and you're left with douro, very much like you'd actually say the phrase in portuguese.
The Romans mined the area for gold.

modern Greek gallikos river derivers from Latin Callicum,
before the name was Εχεδωρος, meaning Ehe-Doro or Dooro or Duro, means 'it has gifts'
cause it was ariver that had gold.