Why is Adam and Eve's expulsion from the Garden of Eden known as the Fall?

In Christianity the fall of man, or the fall, is a term used to describe the transition of the first man and woman from innocent obedience to God to a state of guilty disobedience.

The expulsion from the garden was a result of the fall expulsion from the garden is not known as the fall. Disobedience to God (sin) is the fall.