I recently heard this expression and it struck me as a little odd.
Do you know why?
Both means two.
"Both cats and dogs are pets."
"Both trees and flowers grow in my garden"
"Both the moon and the stars came out last night"
Whenever you want to talk about two things
you can say both.
So why did this expression strike me as being odd?
It was basically saying: "Two of these two"
If you want to use both you don't need to add "two".
"Both of these books are very interesting to read."
If you want to use two you could say:
"These two books are very interesting to read"