Where does “Peloponnesus” come from?

Peloponnesus (Latin) comes from Ancient Greek Πελοπόννησος, from Ancient Greek νῆσος — island.

Ancestry of “Peloponnesus”, step by step

Step	Language	Word	Meaning
1	Ancient Greek	Πελοπόννησος	—
2	Ancient Greek	νῆσος	island

Peloponnesus — Etymology, Origin & Word History | Etymology Explorer