Secret police operating in the USSR 1917–23. It originated from the tsarist Okhrana (the security police under the tsar 1881–1917), and became successively the OGPU (GPU) 1923–34, NKVD 1934–46, MVD 1946–53, and the KGB from 1954.
The name is formed from the initials che and ka of the two Russian words meaning “extraordinary commission”, formed for “the repression of counterrevolutionary activities and of speculation”, and extended to cover such matters as espionage and smuggling.