Where does “ন-” come from?

ন- (Assamese) comes from Sanskrit न, from Proto-Indo-Iranian ná, from Proto-Indo-European né — not; no.

ন- (Assamese): not

Definitions

Step	Language	Word	Meaning
1	Sanskrit	न	no, not; no, not, none, no one, nothing, never,...
2	Proto-Indo-Iranian	ná	no, not
3	Proto-Indo-European	né	not; no

ন- — Etymology, Origin & Word History | Etymology Explorer