Duff Kerrigan is a fictional detective featuring in a series of 21st-century detective stories by Jim Ingraham.
That doesn't seem like a very common name, and yet it appears in exactly the same form in another place: a piece of graffiti from 1895 on an ancient Greek temple near Athens (source of image):
Is there any connection between these two occurrences of the same name? Is there any evidence that Jim Ingraham was inspired by the Sounion graffiti to create his character? Or is it just a big coincidence?