Paddy Fallon was an individual in a detective novel Data was reading in early 2364 to become more prepared for a Dixon Hill adventure. In this novel, Fallon was a brother of Cap Fallon and a friend of Jim Tierney. (TNG: "The Big Goodbye")

This character was only mentioned in writing.
The pages seen in the episode were actually from the detective novel, The Listening Man, by author John A. Moroso. This novel was published in 1924. Information on Paddy Fallon was from pages 109, 112-113, 128-129, and 130-131.