Why is it called the Cold War?

The 45-year standoff between the West and the USSR.

In 1945, shortly after the United States dropped the atomic bomb on Hiroshima and Nagasaki, British writer George Orwell used the term "Cold War" in an essay that explored what the atom bomb implied for international relations. The atom bombs killed more than 100,000 Japanese citizens, disclosing a destructive power so terrifying that Orwell envisioned it would discourage open warfare among great powers, leading instead to "a state which was at once unconquerable and in a permanent state of 'cold war' with its neighbours".

The term "cold war" had existed since the 1930s to describe increasingly fraught relationships between European countries. The 45-year standoff between the West and the USSR ended when the Soviet Union dissolved. Consequently, the term "Cold War" became a shorthand to describe the ideological struggle between capitalism in the West and communism in the East. The long-lasting and continuing confrontation between the Soviet Union and the United States, starting from 1945 was called the Cold War because neither the Soviet Union nor the United States officially declared war on each other.

References:

https://www.nationalgeographic.com/culture/article/cold-war