The term "Big Bang" was actually used to help discredit the idea!
In the 1960s, a commotion in Astronomy was occurring. Part of this happened at Bell Laboratories. Physicists Arno Penzias and Robert Wilson discovered weak microwave radiation being received on Earth from every direction in the sky, 24 hours a day.
They could not attribute it to any particular body in the universe. Together with astronomers at Princeton University, they concluded that this radiation was the echo of the explosion from which the Universe formed: the Big Bang.
More and more evidence for the Big Bang accumulated throughout the 20th century. There are now few professional astronomers who seriously believe anything else.
[Related Topic: Microwaves]