Where does “HNHTWN-tn'” come from?

HNHTWN-tn' (Pahlavi) comes from Proto-Iranian ni-, from Proto-Indo-Iranian ní, from Proto-Indo-European ni — down.

Ancestry of “HNHTWN-tn'”, step by step

StepLanguageWordMeaning
1Proto-Iranianni-down
2Proto-Indo-Iraniannídown, downwards; in, into
3Proto-Indo-Europeannidown
Every word from Proto-Indo-European ni →Every word from Proto-Indo-Iranian ní →Every word from Proto-Iranian ni- →