You know what it looks like… but what is it called?
TAKE THE QUIZ“of-the-heart”
The following 2 entries include the term of-the-heart.
cockles of the heart
noun phrase: the core of one's being —usually used in the phrase warm the cockles of the heart
matters/affairs of the heart
idiom: romantic matters/affairs
Love words? Need even more definitions?
Merriam-Webster unabridged