Literally meaning "big name". In the Tokugawa period, the Daimyo were all the samurai whose revenues were superior to 10,000 koku of rice (or about 50,000 bushels or 1,510,000 liters - one koku of rice is enough to feed one person for one year).
Daimyo had domains with retainers (samurai) onto which they had considerable power. The few hundreds Daimyo domains of the Tokugawa age were reorganized into prefectures in the late 1800's by the Meiji administration.
