late 14c., "daily, happening every day," from Late Latin diurnalis "daily," from Latin dies "day" + -urnus, an adjectival suffix denoting time (compare hibernus "wintery"). Dies "day" is from PIE root *dyeu- "to shine" (source also of Sanskrit diva "by day," Welsh diw, Breton deiz "day;" Armenian tiw; Lithuanian diena; Old Church Slavonic dini, Polish dzień, Russian den).
From early 15c. as "performed in or occupying one day;" 1620s as "of or belonging to the daytime (as distinguished from nocturnal). Related: Diurnally.
<a href="https://www.etymonline.com/word/noctidial">Etymology of noctidial by etymonline</a>
Harper, D. (n.d.). Etymology of noctidial. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/noctidial