If you have watched 'Jack Reacher', starred by Tom Cruise (as Jack Reacher) and Rosamund Pike (as Helen Rodin), you couldn't have missed the villain who choose to call himself 'The Zek', once an inmate in a Russian prison camp in Siberia.
That would have been The Gulag, the Soviet forced labour camp system, that was a mirror-image of the concentration camps or Konzentrationslagers in Nazi Germany. The Gulag institution was officially closed in 1960, which means that 'The Zek' might be a survivor of these forced labour camps.
You should have read the 'The Gulag Archipelago', a three-volume book written by Russian ex-prisoner, writer and historian Aleksandr Solzhenitsyn (1918-2008), to really understand the horrors and the hardship that prisoners in the Gulag had to endure.
Russian prisoners were put to work as forced labourers and their first major project was the digging of the White Sea–Baltic Canal, that connected the White Sea (in the Arctic Ocean) with the Baltic Sea. The entire canal was constructed in just twenty months, between 1931 and 1933, almost entirely by manual labor. Beginning and ending with a labor force of some 125,000, possibly as much as 240,000 laborers died.
Understandably, zaklyuchyonny kanaloarmeyets was usually abbreviated to 'з/к' in official paperwork and pronounced as 'zeka', which gradually transformed into 'zek'.
For the very same reason, Konzentrationslager in Nazi Germany was shortened to KZ-lager.