'bacchanal' originates from Latin, specifically the word 'Bacchanālia', related to 'Bacchus' (the Roman god of wine), where the element 'Bacch-' referred to that god and the festival name denoted rites in his honor.

'bacchanal' changed from Latin 'Bacchanālia' (name for the festivals) and the Greek sacred-drama word 'Bakkhai' (followers of Dionysus), passed into Late Latin/Medieval usage and eventually became the modern English word 'bacchanal' (singular) and 'bacchanals' (plural).

Initially, it meant 'the festivals or rites in honor of Bacchus (Dionysus)'; over time it evolved to mean 'riotous, drunken revelry' and then 'a person who takes part in such revelry'.