As far as they were concerned it was a fourth-century innovation adapted in part from the pagan festival of Saturnalia.
That is the sense of the Saturnalia, of Mardi Gras and of these moments of entertainment.
time of merrymaking, 1590s, from Latin Saturnalia, ancient Roman festivals of Saturn (held in December), a time of merrymaking for all, from neuter plural of adjective Saturnalis "pertaining to Saturn," from Saturnus (see Saturn). They correspond to the Greek Kronia. The extended sense of "period of unrestrained revelry" is first attested 1782. Related: Saturnalian.