When someone asks for your John Hancock, it means they want your signature.
John Hancock was the first man to sign the United States’ Declaration of Independence in 1776. Knowing that signing this declaration could mean his imprisonment or even death, John Hancock boldly wrote his name in large letters, declaring, “There, I think King George should be able to read this.”
When someone asks for your John Henry, it means they want your signature.
The use of John Henry to refer to a signature became popular in the western United States, fifty years after John Hancock signed the Declaration of Independence. Signing your John Henry is cowboy slang. While there is an American Tall Tale about John Henry, the steel-driving man who outperformed a steam-driven machine, this character does not seem to be related to the phrase sign your John Henry, as the story dates to a time after cowboys began referring to signing your John Henry. Of the two phrases, John Hancock is the most used term, today.
Say what you mean, mean what you say, and sign your John Hancock. (Huffington Post)
Eight children wore fresh baseball caps with hanging price tags and the John Hancock of a famous player – in this case, a Los Angeles Angels of Anaheim pitcher named Garrett Richards — scrawled atop the brims. (The Press Enterprise)
You Can Put Your ‘John Hancock’ on the Declaration of Internet Freedom (Forbes)
But if you don’t want to hunt down a fax machine or mess with scanners, consider adding your John Hancock via DocuSign’s mobile app. (The Washington Post)
Try putting your John Henry on a golf ball some time — it’s not the easiest thing to do. (The Des Moines Register)