At The Drop of a Hat

Etymology:

• Historically back to few years ago, it was stated that when someone drop hat, it would be considered as the signal of starting the match or contest immediately. As nowadays we say ‘get set and go’ and ‘ready, set, go!’, similarly, ‘at the drop of a hat’ is used for such task, event, act, or work we are keen to do immediately without any delay. So we can say that, it is done, at the drop of a hat.