There right next to the muscels, according to this pretty lady from Dublin. I hear they are pretty fresh as she’s really emphasizing the fact that they are still alive-o.

It’s referring to the ventricles, which look similar to a cockle shell (a type of shellfish).

Not sure but I got kicked in the cockles once and it hurt like a dickens. I mean not as much as being kicked in the dickens of course.

I take it from the comments that no one here, but OP and me, have heard the Denis Leary song?

There are two parts to this. The first is the word “cockles” and the second is using the word within the specific context of “the heart”.

AFAI remember, this is from medieval times. Cockle was a term given to any part of the body that was sensitive or easily affected. It was pretty widely used at the time.

Medieval doctors didn’t really view the heart as a single organ but the source of all of human emotions and the place where our soul resides. So emotions like love joy and grief lived in a specific, sensitive part of the heart called the cockles. And so the cockles was a small delicate region of the “heart”, and the phrase cockles of the heart referred to this emotional center.

As I understand it, they’re next to the muscles, and are alive alive - oh

A cockle is a type of shellfish. I don’t know how the association with the heart was formed, but it must be old—the Latin name for the order is “Cardiida”.