A hierarch is literally a "sacred ruler" — and the related word hierarchy was invented to describe the ranked orders of angels.
A chief priest, archbishop, or other religious leader; a person who holds a high position in a hierarchy.
From Medieval Latin hierarcha, from Greek hierarkhēs (ἱεράρχης), meaning leader of sacred rites, from hieros (ἱερός, sacred, holy) + arkhein (ἄρχειν, to rule, to lead). Key roots: *ish₁ros (Proto-Indo-European (uncertain): "holy, sacred"), *h₂erḱ- (Proto-Indo-European: "to hold, to contain, to guard").
The word hierarch literally means "sacred ruler" in Greek, and it originally referred specifically to the leader of religious ceremonies. The related word hierarchy was coined by Pseudo-Dionysius the Areopagite around 500 CE to describe the ranked orders of angels — it literally means "rule by the sacred." The concept was then applied to church organization and eventually to any ranked system, which is why your office org chart owes its vocabulary