The U.S. Navy's Spruance class destroyers were the first gas turbine-powered ones to enter service, although they have all been retired now. (The basic hull design lives on in a few Aegis class missile cruisers, though.)
Anyway, destroyers are named after American and Navy heroes and when it came time to select a name for DD 981 in the mid-1970s, the name John Hancock was chosen. Hancock was one of the signers of the Declaration of Independence and signed the document with a flourish.
When it came to painting the name of the USS John Hancock on the stern of the ship, someone came up with the excellent idea to scale up John Hancock's signature from 1776.
