The families who would be able to receive one character (Henki [a portion of the name of a person in high rank, which is given to a retainer to show their subordination]) of a Shogun's name was predetermined by the social standing of a family.
将軍の一字（偏諱）を拝領する家柄は固定していたので、元来「定」の字を使用していた大名が遠慮して改名するという現象を生じた（例：久松氏）。