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.
(..) I'd like to say it's nostalgia, but every time I think of throwing anything away, my ears start to ring, and I get butterflies in my stomach. And then it feels like the butterflies get eaten by rats, and then, the-the rats get eaten by... (..)2016 TvShow: The Big Bang Theory Title: The Solder Excursion Diversion Season: 9 Episode 19