Here's a beguiling irony: Toyotomi Hideyoshi (1536-98), architect of Tokugawa Japan's rigid class structure and the author, in 1587, of a firm ban (not firmly enforced) on surnames for commoners, was himself born without a surname.
"Toyotomi," the family name under which his memory survives, was the last of several surnames he more or less arbitrarily gave himself. He took it (or rather had the powerless Emperor confer it upon him) a mere two years before he issued the ban. Its meaning is "rich abundance."
Similarly spurious is the appropriation by Matsudaira Takechiyo (1542-1616), aka Matsudaira Jirosaburo Motonobu, aka Matsudaira Kurandonosuke Motoyasu — such name changes are by no means unusual — of the Tokugawa surname in 1567. History knows him as Tokugawa Ieyasu, founder, in 1603, of the Tokugawa Shogunate.