Where does “ná” come from?

ná (Proto-Indo-Aryan) comes from Proto-Indo-Iranian ná, from Proto-Indo-European né — not; no.

Ancestry of “ná”, step by step

StepLanguageWordMeaning
1Proto-Indo-Iraniannáno, not
2Proto-Indo-Europeannénot; no
Every word from Proto-Indo-European né →Every word from Proto-Indo-Iranian ná →