late 15c., "a guide," from Anglo-French directour, French directeur, agent noun from Latin dirigere "set straight, arrange; give a particular direction to," from dis- "apart" (see dis-) + regere "to direct, to guide, keep straight" (from PIE root *reg- "move in a straight line").
Corporate sense of "one of a number of persons having authority to manage the affairs of a company" is from 1630s; theatrical sense of "the leader of a company of performers" is from 1911.
adjectival word-forming element, variant of -al (1) with connective -i-. From Latin -ialis, in which the -i- originally was from the stem of the word being attached but later came to be felt as connective.
<a href="https://www.etymonline.com/word/directorial">Etymology of directorial by etymonline</a>
Harper, D. (n.d.). Etymology of directorial. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/directorial