Great name. It was the title of a feudal Japanese lord, maybe a provincial governor or the head of a large or powerful clan. A sucessful Daimyo would hire Samurai as his body guards and his army. The Daimyo were not originally of the imperial court nobility. Their origin comes from the various military governments.
The term generally applied to those lords who governed lands produced at least 10,000 koku of rice annually (one koku was enough rice to feed one man for one year).