- The name William is composed of two parts from the Old German language: willa (for will or resolve) and helma (for helmet). One way these were used together was to denote a soldier or guardian, or resolute protector.
- For many years after the Norman conquest in AD 1066, many English boys were given some form of the name of William the Conqueror, the first Norman King of England. Many generations since have continued to use this name.
- Abbreviations and derivations of this name include Liam, Will, Bill, Willie, Billy, Wilhelm, Guillaume, Guillermo
- The firstborn son of Prince Charles and Princess Diana was named William (born William Arthur Philip Louis in 1982)
- Some famous people named WIlliam (many using Bill or Billy): Bill Clinton, Bill Murray, Billy Crystal, Billy Joel, Bill Gates, William Shatner, Bill Maher, William Shakespeare, Billy Bob Thornton, Billy Idol, William McKinley, William Howard Taft, William H. Macy, Billy Ray Cyrus, Billy Corgan, William Hurt, Bill Nighy, William Henry Harrison, William S. Burroughs, Billy Dee Williams, Bill Nye, William Faulkner
