Tiddy Mun was a legendary bog spirit in Lincolnshire, England, who was believed to have the ability to control the waters and mists of The Fens of South Lincolnshire and The Carrs of North Lincolnshire. The belief in Tiddy Mun was first documented in June 1891 in an article by M. C. Balfour in the Folklore Society journal Folk-Lore. In the article she recalls a story, collected in the Ancholme Valley, told to her by an older person who spoke of a curse of pestilence that had been cast upon his village by the Tiddy Mun, who was angered at the draining of the Fens by the Dutch, led by Cornelius Vermuyden, in the seventeenth century. According to the story the Tiddy Mun was eventually placated after the villagers gathered at twilight at the time of the new moon, poured buckets of water into the dyke and apologised for the damage caused.
He was not exclusively malevolent; if the Fens flooded and the waters reached the villages, people would go out at night and call Tiddy Mun wi'out a name, tha watters thruff! ("Tiddy Mun without a name, the water's through!) until they heard the cry of a peewit, and the next morning the waters would have receded.
Drainage Mills in the_Fens, Croyland, Lincolnshire