Definition & Meaning of "big deal"

What is the origin of the idiom "big deal" and when to use it?

The idiom "big deal" is used to describe something of high priority or special importance, and it is typically used in a sarcastic or dismissive manner to downplay the significance of an event or situation. Its origin likely stems from the use of "big" to emphasize importance, while the "deal" aspect reflects the colloquial nature of the expression.