Where does “nindā” come from?

nindā (Pali) comes from Sanskrit निन्दा, from Proto-Indo-European h₃neyd- — to revile, insult.

Ancestry of “nindā”, step by step

Step	Language	Word	Meaning
1	Sanskrit	निन्दा	blame; reproach; censure
2	Proto-Indo-European	h₃neyd-	to revile, insult