Where does “Ἀρκτοῦρος” come from?

Ἀρκτοῦρος (Ancient Greek) comes from Ancient Greek οὖρος, from Latin ūrus, from Proto-Germanic ūraz, from Proto-Indo-European ūsr- — aurochs; buffalo.

Ἀρκτοῦρος (Ancient Greek): Arcturus, a bright star in the Boötes constellation

Definitions

Arcturus, a bright star in the Boötes constellation

Ancestry of “Ἀρκτοῦρος”, step by step

Ἀρκτοῦρος traces back through 3 separate lines of ancestry.

via Ancient Greek οὖρος

Step	Language	Word	Meaning
1	Ancient Greek	οὖρος	fair wind; guardian, watcher; aurochs, "Bos...
2	Latin	ūrus	aurochs (Bos primigenius)
3	Proto-Germanic	ūraz	aurochs
4	Proto-Indo-European	ūsr-	aurochs; buffalo

via Ancient Greek ἄρκτος

Step	Language	Word	Meaning
1	Ancient Greek	ἄρκτος	bear; the north
2	Proto-Indo-European	h₂ŕ̥tḱos	bear
3	Proto-Indo-European	h₂r̥tḱós	destroying

via Ancient Greek ᾰ̓́ρκτος

Step	Language	Word	Meaning
1	Ancient Greek	ᾰ̓́ρκτος	bear

Words derived from “Ἀρκτοῦρος”

Every word from Proto-Indo-European ūsr- →Every word from Proto-Germanic ūraz →Every word from Latin ūrus →