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.