Śmigus-dyngus or lany poniedziałek. Wet Monday (Easter Monday) in Poland. Originally this Slavic custom meant whipping each other with birch twigs and throwing water at each other which used to symbolize the spring cleansing. This ritual was already in custom in 750, over 200 years before Poland officially adopted Christianity. Dyngus and Śmigus were twin pagan gods; the former representing water and the moist earth and the latter representing thunder and lightning .