Where does “douro” come from?

douro (French) comes from Spanish duro, from Old Spanish duro, from Latin dūrus, from Proto-Italic dūros, from Proto-Indo-European duh₂-ró-s, from Proto-Indo-European dweh₂- — far; long.

douro (French): a Spanish coin worth five pesetas

Definitions

a Spanish coin worth five pesetas

Ancestry of “douro”, step by step

Step	Language	Word	Meaning
1	Spanish	duro	hard; firm, solid; hard, difficult
2	Old Spanish	duro	—
3	Latin	dūrus	—
4	Proto-Italic	dūros	—
5	Proto-Indo-European	duh₂-ró-s	long, far
6	Proto-Indo-European	dweh₂-	far; long

Every word from Proto-Indo-European dweh₂- →Every word from Proto-Indo-European duh₂-ró-s →Every word from Proto-Italic dūros →