Dyngus Day celebrations are widespread and popular in Buffalo, New York, Wyandotte and Hamtramck in Michigan; South Bend and La Porte in Indiana; and Hanover, New Hampshire. What it actually is for all intents and purposes is a license to go out and get hammered after some people's Lenten abstinence.
Śmigus-Dyngus (also known as lany poniedziałek, meaning "Wet Monday") is a celebration held on Easter Monday in Poland. It is also observed by Polish diaspora communities, particularly among Polish Americans, who call it Dyngus Day. Traditionally, boys throw water over girls and spank them with pussy willow branches on Easter Monday, and girls do the same to boys on Easter Tuesday. This is accompanied by a number of other rituals, such as making verse declarations and holding door-to-door processions, in some regions involving boys dressed as bears.
~~~What About Bob? (1991)