“We produce a wide variety of food on our farm.” “Boy, I'll say — everything from melons to beans to meat!”
Etymology: based on the full form I will say the same thing
I'll say
That's very true; I really agree; absolutely. A: "Wow, this bookshop has everything." B: "I'll say! I didn't even know copies of this book still existed!"A: "Did Billy enjoy his first day at school?" B: "I'll say he did! He didn't even want me to take him home at the end of the day."
I'll say
Absolutely, I strongly agree. For example, Did you enjoy the film?-I'll say. This phrase is generally used alone and for emphasis. [First half of 1900s] For a synonym, see you can say that again.