Fans were originally introduced from China in the Nara period but during the Heian period the Japanese invented a collapsible fan called a sensu using a thin sheet of cypress wood. They became very popular among aristocrats who used them for ceremonies and as accessories and some were even exported to China. Gradually, warriors started using them as commanding sticks and ordinary people began using sensu made of paper and bamboo in the Edo period. Since a sensu spreads out wide toward the end, people consider them to be symbols of good luck.
An English Introduction to Japan and Its people (アルク)