What does Japanese Naked Hip Festival mean?

Japan's traditional summer festival (Hakata only won a hat), I will call it Naked Hip Festival for the time being! Because each of them has to be naked.

Every summer, from July of 1 year to June of 15, I hear the cries of (Ouisha-Ouisha) in the street, and see a group of naked men in national costumes screaming in the street with mountains (decorations like mountains) weighing about 1 ton on their shoulders. From time to time, people on the side of the road prepared buckets to splash water on the men running over.