I have heard many people say things like: something was dear to their heart;
they just can't pour their heart into something, so on and so forth & that many people included me too.
If you give it more thought, heart really doesn't hold anything does it?
It's your brain that saves all the information, expressions, feelings etc.
Can you imagine a world where people would say "I love you with all my brain", "you broke my brain" while pointing to their head??