Take this medication 'on an empty stomach'. [=when your stomach is empty because you have not eaten for a time]
When I had the flu, just the thought of eating made me 'sick to my stomach'. [='nauseous']
She felt a flutter in 'the pit of her stomach' when he walked through the door.
(..) You leave public opinion to me. You better go back into the Senate. I hit him from the floor with everything I knew. I haven't got the stomach for it. If he starts convincing those senators, you might as well blow your brains out! This is the works! Either we're out of We can't stop at anything (..)1939 Mr. Smith Goes to Washington