According to the most popular legend, during the Ottoman times of the territory, people from Mohács fled the town, and started living in the nearby swamps and woods to avoid Ottoman (Turkish) troops. One night, while they were sitting and talking around the fire, an old Šokac man appeared suddenly from nowhere, and said to them: "Don't be afraid, your lives will soon turn to good and you'll return to your homes. Until that time, prepare for the battle, carve various weapons and scary masks for yourselves, and wait for a stormy night when a masked knight will come to you."
He disappeared as suddenly as he arrived. The refugees followed his orders, and some days later, on a stormy night, the knight arrived. He ordered them to put on their masks and go back to Mohács, making as much noise as possible. They followed his lead. The Turks were so frightened by the noise, the masks, and the storm in the night, that they thought demons were attacking them; and they ran away from the town before sunrise.
In the older, less popular story, the busós are scaring away not the Turks but Winter itself. --wikipedia