The term 'Of the Matter Heart' is a phrase that has been used in literature and popular culture for centuries. It is often used to describe a person's innermost feelings and emotions. The crossword solution for this term is 'NUB', which is an acronym for 'Nothing Under the Bridge'. This phrase is used to describe a situation where there are no secrets or hidden agendas, and everything is out in the open. It is also used to describe a situation where all parties involved are honest and forthright with each other.