The first use of authoritarian is in 1852, in the writings of AJ Davis apparently. Here's the quote:

1856 A. J. Davis Penetralia 129 Does any one believe that the Book is essential to Salvation? Yes; there are many externalists and authoritarians who think so.

Authoritarian was also increasing in usage well before the cold war, beginning around 1910 or so. An example from Nationalism and Culture by Rudolf Rocker, written in 1933:

Nietzsche also had a profound conception of this truth, although his inner disharmony and his constant oscillation between outlived authoritarian concepts and truly libertarian ideas all his life prevented him from drawing the natural deductions from it.

That's a thoroughly modern use of the word authoritarian, written almost 15 years before the start of the cold war. Authoritarian is used to describe those who support hierarchial systems of government. That's the short and sweet of it, perhaps not a perfect dictionary definition but it illustrates the distinctive bit. Auth-left ideologies get equivocated with fascism because there's an undeniable ideological throughline between the two, no matter how much they hate each other.

"The working class [...] cannot be left wandering all over Russia. They must be thrown here and there, appointed, commanded, just like soldiers [...] Compulsion of labour will reach the highest degree of intensity during the transition from capitalism to socialism [...] Deserters from labour ought to be formed into punitive battalions or put into concentration camps.'

Trotsky wrote that. It may not be 1:1 but the similarities between his ideas and those.of fascists are pretty obvious.

All of this, written before the cold war. Tell me again how authoritarian is a made up word that serves only to slander "communists"?