From early in his life he was known as "Shamus" to his friends and family, as he didn't like to use his given name of James due to the fact that it reminded him of his father, also called James, who abandoned him at a young age. However, he was still credited as "James Culhane" through much of his early career, as it was considered unprofessional to be credited under anything except your birth name among the major animation studios.