Dictionary.com lists seven different meanings for the word 'hierarchy', including "government by ecclesiastical rulers" and "government by an elite group". But the fourth definition is perhaps the one that comes closest to the original meaning: "an organized body of ecclesiastical officials in successive ranks or orders".
In ancient Greece, a hierarch was a high priest, and this is one way in which dictionary.com defines the word 'hierarch' today. In Mediaeval Latin, the word came to mean rule by, or the power of, a high priest; its use in the sense of "any system of persons or things ranked one above another" (the first of dictionary.com's seven definitions) originally referred to the ranking of priests.
Because of the number and varieties of meanings, my advice (for what it's worth) would be to avoid asking the meaning of this word in quizzes, unless you're prepared to accept any answer that refers to one or more priests.
© Haydn Thompson 2018