Tokugawa Ieyasu
In 1562, he changed his name to Matsudaira Motoyasu.  The second syllable -- -yasu -- comes from the name of his grandfather Kiyoyasu.  A few months later, he changed his first name to the one by which he is known today.  The first syllable --  Ie-'' -- comes from the last part of the name of Minamoto Yoshile, who was a famous ancestor.  He received permission from the emperor to change his family name from Matsudaira to Tokugawa.