John Hancock, president of Congress, was the first to sign the Declaration of Independence, writing his name in large, plain letters, and saying: "There; John Bull can read my name without spectacles. Now let him double the price on my head, for this is my defiance." [Hélène Adeline Guerber, "The Story of the Thirteen Colonies," New York, 1898]
The family name is attested from 1276 in Yorkshire, a diminutive (see cock) of Hann, a very common given name in 13c. Yorkshire as a pet form of Henry or John.