Where does “ochtar” come from?

ochtar (Old Irish) comes from Proto-Celtic ouxsterom, from Proto-Indo-European h₃ewp-s- — high.

ochtar (Old Irish): top, surface, cream

Definitions

Step	Language	Word	Meaning
1	Proto-Celtic	ouxsterom	—
2	Proto-Indo-European	h₃ewp-s-	high

ochtar — Etymology, Origin & Word History | Etymology Explorer