hierarchy

First recorded in 1350–1400; Middle English jerarchie, from Middle French ierarchie, gerarchie, from Medieval Latin (h)ierarchia, from Late Greek hierarchía “stewardship of sacred rites, rule or power of the high priest,” equivalent to hier(o)- “holy, sacred” + -archía, a combining form meaning “rule”; see hier(o)-, -archy

Hierarchy comes ultimately from Greek hierarchía “stewardship of sacred rites,” a derivative of hierárchēs “high priest, leader of sacred rites,” via Medieval Latin (h)ierarchia.
The Medieval Latin word originally meant “rank or dignity of a hierarch (high-ranking religious leader)” in a system devised in the late 5th or early 6th century by the mystical theologian and philosopher Pseudo-Dionysius. The Greek word hierarchía is formed from hierós “holy, dedicated to a god, sacred, strong, excellent, glorious” and a derivative of the verb árchein “to be first, begin, rule.”
The earliest occurrence of hierarchy in English dates from the late 14th century in the sense “one of the three divisions of the angels into higher and lower ranks.” This meaning was quickly extended to other supernatural entities, and finally, in the 16th century, to “rule or dominion in holy matters, rule or government by priests, a system of ecclesiastical rule.” The sense “a group of people, plants, animals, or things ranked in grades, orders, or classes” dates from the 17th century.

C14: from Medieval Latin hierarchia, from Late Greek hierarkhia, from hierarkhēs high priest; see hiero-, -archy