slang One's signature. A variant of the more common "one's John Hancock," likely as a means of shortening it in everyday speech. John Hancock was an influential figure in the American Revolution who is now known for his especially large and legible signature on the Declaration of Independence. As soon as you put your John Henry on these papers, you'll be the proud owner of a brand new car! We're going to need your John Henry on this contract to make the deal official.