Dear Steve Kloves,
I believe that there are a great many terms that you could use when describing the upper left area of the torso, depending on what you are aiming for. Ribcage, for example. Breast. Chest. Bosom. Lungs. Left boob. Rump. You get my drift. If absolutely necessary, even 'heart' would do.
So why, oh why, do the characters in the HP movies point to the general body area described above and say things like 'Harry, he will live on / you will feel it / I will always be / etc. IN HERE'??? ALL. THE. TIME.
It feels like they're constantly talking to four-year-olds. I fully believe that an averagely intelligent young adult like Harry Potter, who has seen quite a bit of the (magical) world, will be aware of the symbolisms generally associated with that roughly fist-shaped, blood-pumping organ usually found in the left side of the thorax.
Sincerely, etc.