Seeing that the topic of the thread was about signatures, you would think when asked "where did it come from" we would be talking about....signatures...
"Cry 'Havoc!' and let slip the dogs of war."
That make it easier?
Well he didn't even quote my signature, all he did was ask where the line of text "I have the best signature" came from.
As for "cry havoc" it was a command in the 18th century with the british used to command soldiers to ransack, and pilage.