Where does “onde” come from?

onde (Czech) comes from Proto-Slavic onъ, from Proto-Balto-Slavic anas, from Proto-Indo-European h₂en — there.

onde (Czech): elsewhere

Definitions

Step	Language	Word	Meaning
1	Proto-Slavic	onъ	he, it, that; that, that over there, yonder
2	Proto-Balto-Slavic	anas	that over there, yonder
3	Proto-Indo-European	h₂en	there

onde — Etymology, Origin & Word History | Etymology Explorer