Where does “ウーラノス” come from?

ウーラノス (Japanese) comes from Ancient Greek οὐρανός, from Ancient Greek ϝορσανός.

Ancestry of “ウーラノス”, step by step

Step	Language	Word	Meaning
1	Ancient Greek	οὐρανός	the vaulted sky, on which the stars were attached...
2	Ancient Greek	ϝορσανός	—

ウーラノス — Etymology, Origin & Word History | Etymology Explorer