Late 16th century; earliest use found in Reginald Scot (d. 1599), writer on witchcraft. From Middle French genethliaque, French généthliaque (noun) astrologer who calculates horoscopes, horoscope, art of calculating horoscopes, speech or poem celebrating a birthday, (adjective) of or relating to birthdays and its etymons post-classical Latin genethliacus (adjective) relating to the casting of nativities, (noun) speech or poem celebrating a birthday and Hellenistic Greek γενεθλιακός (adjective) belonging to a birthday, (noun) person who calculates nativities from ancient Greek γενέθλιος of or belonging to one's birth, of one's race or family (from γενέθλη race, stock, birth + -ιος, suffix forming adjectives) + -ακός.