Nickname of Prince William Frederick (1776–1834), Duke of Gloucester; also of William IV of the United Kingdom (1765–1837)
Silly Billy (plural Silly Billies)
- An epithet used in mild teasing for a silly person, or one who has just done something of an foolish nature.
Denis Healey, British politician, was known for using the term as a catchphrase. This originated with Mike Yarwood's famous impression of him, although he later used it himself in parliament.