"one who rules in holy things," 1570s, from Medieval Latin hierarcha, from Greek hierarkhia, from hierarkhes "leader of sacred rites, high priest" (see hierarchy).
-al 1
suffix forming adjectives from nouns or other adjectives, "of, like, related to, pertaining to," Middle English -al, -el, from French or directly from Latin -alis (see -al (2)).