Sorry to burst your bubble, but as far as I've been able to determine the term "Tsar Bomba" was only used in the post-Soviet era.

Internally the Soviets called it "Product 202" or "Big Ivan" (supposedly). Only later did it get "Tsar Bomba" attached to it in analogy to the Tsar Bell and the Tsar Cannon, two technological creations that were impressively large but could not really be used. (The Soviets in the 1960s did think that the 50 megaton bomb could be used, though it was a waste of resources and very hard to deliver.)

Prior to the 1990s it was called "the 50 megaton bomb" and other similarly uninteresting names in the West.