Sando means "three times," "thrice". So why is this mushroom-shaped hat called the sando kasa? In the Edo Era (1603-1868), Osaka merchants established a courier service connecting Edo, Kyoto, and Osaka. Letters and parcels were sent three times a month, on the 2nd, 12th, and 22nd, and were delivered by "postmen" wearing hats like the one above. In this way the hat came to be known as the "thrice sedge hat". The sando kasa became widely adopted for the protection it offered against rain and sun, shielding the heads of travelers and farm laborers as well as the postmens' pates.