Where does “frateso” come from?

frateso (Ido) comes from Ido frato, from Esperanto frato, from Latin frāter, from Proto-Italic frātēr, from Proto-Indo-European bʰréh₂tēr — brother.

frateso (Ido): siblinghood

Definitions

Step	Language	Word	Meaning
1	Ido	frato	sibling
2	Esperanto	frato	brother; sibling
3	Latin	frāter	—
4	Proto-Italic	frātēr	brother
5	Proto-Indo-European	bʰréh₂tēr	brother

frateso — Etymology, Origin & Word History | Etymology Explorer