Short answers, pulled from the story.
Giovanni Amendola first used the term in 1923 to define a system where the supreme leader exercises total power over political, military, economic, and social life. Italian Fascists later adopted this label as an official self-description for Fascist Italy between 1922 and 1943.
Carl Joachim Friedrich and Zbigniew Brzezinski published Totalitarian Dictatorship and Autocracy in 1956 to establish a standard model including an elaborate guiding ideology, a one-party state, state terrorism, monopoly control of weapons, monopoly control of mass communications media, and a centrally directed planned economy.
The label became a critical tool only after World War II when Western political science began comparing different dictatorships. The term gained legitimacy in 1939 with the Molotov, Ribbentrop Pact which allowed scholars to present Stalin and Hitler as twin dictators.
Revisionist historians argue that institutions often escaped the control of the center and that many purges were local initiatives leaders could not fully control. They emphasize history from below and note that citizens collectively resisted by refusing to work efficiently and migrating by the millions.
In the 21st century the term became applied to Islamist movements and their governments while Stephane Courtois edited The Black Book of Communism in 1997 to stress structural homology of totalitarian systems. John Connelly wrote in 2010 that the old 1950s theory is defunct among scholars while the word remains functional for describing rulers perceived as totalitarian.