Cast Iron Stomach noun phrase
If someone has a cast iron stomach, they have a strong stomach that can digest unusual food and even bad food without being ill.
Jimmy must have a cast-iron stomach, when he drank milk with lime juice and felt perfectly fine afterward.
You must have a cast-iron stomach if you eat this stuff.
To have a strong stomach against bad or unusual food
This idiom became widespread around the early 1900s since cast-iron is a type of metal that commonly used in creating cooking utensils. Pans that are made with cast-irons are tough and resilient hence, making the meaning of the idiom.
1. A pill or tablet that is hard for someone to swallow because of its large size
2. An fact, claim, proposal, etc. that is very difficult to believe or accept
1. The vet gave my adorable puppy a horse pill and he spat it out immediately.