Question - why is it that human heart is compare to its fist?

The human body both internally and externally has easy to understand measurements, once you know the system, which is not based on anything we already know.

For example, the length between your forefinger and thumb when held together is the same length as your nose.

The measurement from the center of your upper chest to the out stretched middle finger of your right or left hand is exactly half your height.

The clenched fist it is believed, is about the same size as the heart of the owner of the hand.

There are many more of these, but as far as I know, no one has put them into an order or given such measurements a name.