Where does “no” come from?

no (Old Portuguese) comes from Old Portuguese eno, from Old Portuguese en, from Latin în, from Latin en, from Proto-Italic en, from Proto-Indo-European h₁én — in.

Ancestry of “no”, step by step

Step	Language	Word	Meaning
1	Old Portuguese	eno	—
2	Old Portuguese	en	in
3	Latin	în	in, at, on, upon, from (space)
4	Latin	en	lookǃ beholdǃ; reallyǃ?; come onǃ
5	Proto-Italic	en	in
6	Proto-Indo-European	h₁én	in

Words derived from “no”

nó
no
pedra no sapato
no limiar de
no entanto
no duro

Every word from Proto-Indo-European h₁én →Every word from Proto-Italic en →Every word from Latin en →