Heart : Hridayam, meaning “Here I am” indicating the Self that exists Here and Now.
Ramana Maharshi’s explanation of Heart
Maharshi: You cannot know it (Heart) with your mind. You cannot realize it by imagination when I tell you here is the centre [pointing to the right side of the chest]. The only direct way to realize it is to cease to fantasize and try to be yourself. When you realize, you automatically feel that the centre is there. This is the centre, the Heart, spoken of in the scriptures as hrit-guhaarul [grace], ullam [the Heart].
Maharshi: I ask you to see where the ‘I’ arises in your body, but it is really not quite correct to say that the ‘I’ rises from and merges in the Heart in the right side of the chest. The Heart is another name for the reality and it is neither inside nor outside the body. There can be no in or out for it, since it alone is.