When you sign your name, that's known as giving your John Hancock.
John Hancock is most famous for his bold1 signature2. On August 2, 1776, he was the first member of the Continental Congress3 to sign the Declaration of Independence4, the document first demanding independence for the United States from the rule of Great Britain. Hancock wrote his name in big, bold letters that day, acting as5 president of the Second Continental Congress. This inspired6 the phrase "give me your John Hancock", meaning "give me your signature".