Where does “octoginta” come from?

octoginta (Latin) comes from Proto-Indo-European oḱtódḱomt, from Proto-Indo-European oḱto(w)-dḱomt — eight-ten.

Ancestry of “octoginta”, step by step

Step	Language	Word	Meaning
1	Proto-Indo-European	oḱtódḱomt	eighty
2	Proto-Indo-European	oḱto(w)-dḱomt	eight-ten

octoginta — Etymology, Origin & Word History | Etymology Explorer