Where does “-eso” come from?

-eso (Ido) comes from Ido esar, from Spanish es, from Latin est, from Proto-Indo-European h₁ésti, from Proto-Indo-European h₁es- — to be.

-eso (Ido): Nominal form of -es-

Definitions

Step	Language	Word	Meaning
1	Ido	esar	to be
2	Spanish	es	is; plural of e
3	Latin	est	third-person singular present active indicative...
4	Proto-Indo-European	h₁ésti	to be
5	Proto-Indo-European	h₁es-	to be