Explanation

The term "Third World" was first used during the Cold War era.

The term was coined in 1952 by French demographer, anthropologist, and historian Alfred Sauvy. 

First World: The allied powers of Western Europe and North America, and their allies.

Second World: Communist countries, allies of the Soviet Union. 

Third World: Underdeveloped countries that remained non-aligned with either the United States or the Soviet Union.