Śmigus-dyngus also lany poniedziałek, meaning "Wet Monday" in Polish; Czech: Oblévačka; Slovak: Oblievačka; Hungarian: Vízbevető; Ukrainian: поливаний понеділок) is a celebration held on Easter Monday mostly in Poland, but also in Czech Republic, Slovakia, Hungary and parts of western Ukraine.
Traditionally, boys throw water over girls and spank them with pussy willow branches on Easter Monday, and girls do the same to boys. 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. The origins of the celebration are uncertain, but it may date to pagan times before 1000 AD; it is described in writing as early as the 15th century. It continues to be observed throughout Central Europe.
The celebration has been traced back to the 14th century but may have earlier, pre-Christian origins involving the celebration of the March equinox; the origins of the word dyngus are obscure as it may come from the German Dingeier ("the eggs that are owed") or Dingnis ("ransom").
The occurrence of the celebration across the western Slav countries (plus Hungary, whose inhabitants' forebears conquered a region that was inhabited by Slavs) suggests a common origin in pagan mythology, most likely a link with the Slavic goddesses of fertility. It may possibly be related to the tradition of watering the Corn Mother, who made crops grow and was represented in the form of a doll or wreath made from corn. This would be symbolically drenched in water and kept over the winter until its grain was mixed with the seed corn in the spring to ensure a successful harvest. In time, the growing influence of Christianity in Poland incorporated the dyngus celebrations, along with other pagan practices, into Christian festivals like Easter Monday.
Some have suggested that the use of water is an allusion to the baptism of Mieszko I, the Duke of Polans (c. 935–992) in 966 AD, uniting all of Poland under the banner of Christianity.The New Cambridge Medieval History, however, suggests it that originated far to the west of Poland and was adopted under German influence.