Littlefinger is the nickname for Petyr Baelish.
Many nicknames drop the final one or two letters and add ether ie/ee/y as a diminutive ending: Davy from David, Charlie from Charles, Mikey from Michael, Jimmy from James, and Marty from Martin
 Introduced in 1996's A Game of Thrones, Littlefinger is the master of coin on King Robert's small council

