The following site does not give an explanation of where the name came from but does explain the game, or at least one version of it: -
http://www.urbandictionary.com/define.php?term=padiddle THE PADIDDLE GAME - A "Padiddle", as any trucker will tell you, is a car with one light out. The first person to see one, calls out "Padiddle"; the person who spots the most wins.
Car Padiddle - 1 point
Semi-truck Padiddle - 2 points
VW Bug Padiddle - 3 points
Taxi Padiddle - 5 points
Farm Equipment Padiddle - 5 points
Boat Padiddle - 5 points
Train Padiddle - 10 points
Helicopter Padiddle - 15 points
School Bus Padiddle - 20 points
Police Padiddle - 25 points
Airplane Padiddle - 100 points