Where does “естьство” come from?

естьство (Church Slavonic) comes from Ancient Greek οὐσία, from Ancient Greek εἰμί, from Proto-Hellenic ehmi, from Proto-Indo-European h₁ésmi, from Proto-Indo-European h₁ēs- — to be.

Ancestry of “естьство”, step by step

Step	Language	Word	Meaning
1	Ancient Greek	οὐσία	that which is one's own, one's substance,...
2	Ancient Greek	εἰμί	To be, exist; live; To be; it is possible
3	Proto-Hellenic	ehmi	to be
4	Proto-Indo-European	h₁ésmi	first-person singular present indicative of...
5	Proto-Indo-European	h₁ēs-	to be

Words derived from “естьство”

естество́
естественный
естествознание
естествоиспытатель

Every word from Proto-Indo-European h₁ēs- →Every word from Proto-Indo-European h₁ésmi →Every word from Proto-Hellenic ehmi →