"'Cicero' was a code name for a spy."

During World War II an Albanian named Elyesa Bazna passed Allied secrets to the Germans for financial gain. As a valet to an English officer based in Ankara, Turkey, he took photographs of classified British documents. He was given the codename 'Cicero' by the Germans in 1943.

You can read Bazna's first hand account, I Was Cicero, at the Free Library.

The Cicero Spy Affair: German Access to British Secrets in World War II by Richard Wires

A fiction film, called Five Fingers, was made in 1951 based on Cicero's spy career.