A time of licensed disorder and misrule. With the Romans it was the festival of Saturn, and was celebrated the 17th, 18th, and 19th of December. During its continuance no public business could be transacted, the law courts were closed, the schools kept holiday, no war could be commenced, and no malefactor punished. Under the empire the festival was extended to seven days.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894