Where does “新潟” come from?

新潟 (Japanese) comes from Japanese 新, from Middle Chinese 新.

Ancestry of “新潟”, step by step

Step	Language	Word	Meaning
1	Japanese	新	a novelty; Short for 新暦 : the Gregorian calendar;...
2	Middle Chinese	新	—

新潟 — Etymology, Origin & Word History | Etymology Explorer