Where does “Danube salmon” come from?

Danube salmon (English) comes from English Salmon, from Middle English samon, from Anglo-Norman saumon, from Old French saumon, from Latin salmō, from Armenian Իշխան, from Old Armenian իշխան, from Undetermined xšāna-.

Ancestry of “Danube salmon”, step by step

Danube salmon traces back through two separate lines of ancestry.

via English Salmon

Step	Language	Word	Meaning
1	English	Salmon	A placename
2	Middle English	samon	Alternative form of samoun
3	Anglo-Norman	saumon	salmon
4	Old French	saumon	salmon
5	Latin	salmō	salmon
6	Armenian	Իշխան	prince, ruler, ishkhan
7	Old Armenian	իշխան	prince, ruler, ishkhan
8	Undetermined	xšāna-	—

via English Danube

Step	Language	Word	Meaning
1	English	Danube	—
2	Middle French	Danube	—
3	Old French	Danube	—
4	Latin	Dānubius	—
5	Proto-Celtic	Dānowyos	—
6	Proto-Celtic	Dānu	—
7	Proto-Indo-European	dʰenh₂-	to set in motion; to flow

Every word from Undetermined xšāna- →Every word from Old Armenian իշխան →Every word from Armenian Իշխան →