The pagan Slavs believed in two gods which, you could call gods of joy.
These gods were named Yarilo and Kupala.
Yarilo might possibly come from 'yarovoi', which was used to signify the
corn sown in spring. 'Yary', another word from which it might have been
derived, means 'ardent, passionate, uncontrolled'. Historians reckon that
both these explanations might be relevant. As he was the god of new life,
but in a sexual way instead of corn. He was described as a young, handsome
man dressed in white. He rode a white horse and held some corn containing
the seed in his left hand. He was told to have been barefooted. Celebrations
to his honor were held every year in spring. For a period of four days they
gathered to eat, drink, dance and play 'satanic games', as some described
it. These festivals were still held by some until the eighteenth century.
Kupala was another divinity of joy. His name derived from the same root
as the word 'kupati' that signified bathing. The cult of Kupala worshipped
water, an element that they considered being sacred. During Kupala's festivals,
held in June, They would bathe in rivers and wash them with the 'dew of
Kupala'. Dew that fell during the night of the festival. Another major part
of the cult was the worship of trees, herbs and flowers. They believed that
during Kupala's night, the trees could disconnect their roots from the earth
and they could then talk to each other in a mysterious language.