Jacob Marley was a character in the Charles Dickens story A Christmas Carol. He was the partner of Ebenezer Scrooge.
When Data was studying method acting in order to understand emotions, he used a holonovel of this story. He recreated Marley's ghost to study fear and how it motivated Scrooge. (TNG: "Devil's Due")
Jacob Marley was portrayed by William Glover who received no credit for this part.