Noun, sing., masc.:
- heart ( )
- midst, inner part ( )
This word in Bible seems to mean the unconscious (as discovered by Freud) part of human mind.
In Bible this word meant the literal heart, but also means people's mind. But accordingly modern science, mind of a man is located in brain not heart.
I know three possible explanations.
The first is that this word should be considered as an homonym meaning both heart and unconscious part of the brain.
The second explanation (not pretending to be scientific): Leukocytes inside heart interact through electromagnetic waves with each other, and this form a form of mind whose location is the heart of a person.
The third explanation (not pretending to be scientific) is that some information is preserved in the heart for the case if the brain is damaged (and it is the last resort, because if the heart itself is damaged the person dies). This by the way explains the rumors that people with transplanted hearts inherit the character of the donor.