1530s (n.), "riotous, drunken roistering;" 1540s (adj.) "pertaining to Bacchus," from Latin bacchanalis "having to do with Bacchus (q.v.). The meaning "characterized by intemperate drinking" is from 1711; the meaning "one who indulges in drunken revels" is by 1812.
Entries linking to bacchanal
Bacchus
Greek god of wine and revelry, a later name of Dionysus, late 15c., from Latin Bacchus, from Greek Bakkhos, which is perhaps related to Latin bacca "berry, fruit of a tree or shrub" (see bay (n.4)), or from an Asian language. He was perhaps originally a Thracian fertility god.