Where does “sesaenta” come from?

sesaenta (Old Portuguese) comes from Latin sexāgintā, from Proto-Indo-European sweḱsḱomt, from Proto-Indo-European swéḱs-dḱomt — six-ten.

Ancestry of “sesaenta”, step by step

Step	Language	Word	Meaning
1	Latin	sexāgintā	—
2	Proto-Indo-European	sweḱsḱomt	—
3	Proto-Indo-European	swéḱs-dḱomt	six-ten

sesaenta — Etymology, Origin & Word History | Etymology Explorer