The legend of St. Urho was the invention of a Finnish-American named Richard Mattson, who worked at Ketola's Department Store in Virginia, Minnesota in spring of 1956. Mattson later recounted that he invented St. Urho when he was questioned by coworker Gene McCavic about the Finns' lack of a saint like the Irish St. Patrick, whose feat of casting the snakes out of Ireland is remembered on St. Patrick's Day.
According to the original "Ode to St. Urho" written by Gene McCavic and Richard Mattson, St. Urho was supposed to have cast "tose 'Rogs" (those frogs) out of Finland by the power of his loud voice, which he obtained by drinking "feelia sour" (sour whole milk) and eating "kala mojakka" (fish soup).
The original "Ode to St. Urho" identified St. Urho's Day as taking place on May 24. Later the date was changed to March 16, the day before St. Patrick's Day. St. Urho's feast is supposed to be celebrated by wearing the colors Royal Purple and Nile Green. Other details of the invented legend also changed, apparently under the influence of Dr. Sulo Havumäki, a psychology professor at Bemidji State College in Bemidji, Minnesota. The legend now states that St. Urho drove away grasshoppers (rather than frogs) from Finland using the incantation "Heinäsirkka, heinäsirkka, mene täältä hiiteen!" ("Grasshopper, grasshopper, go from hence to Hell!"), thus saving the Finnish grape crops.