Heart
The heart means love. A good heart means love to the Lord and to the neighbor, while a hard or stony heart means the love of self or the world -- riches and things. When the psalmist asks the Lord to search his heart, he wants the Lord to see what it is that he loves. And we are what we love. What we eat may form our earthly body, but it's only temporary, what we love forms our spiritual body, beautiful or ugly as we have chosen. It's interesting to note that the first multi-cellular motion of our embryo is the pulsating that starts in a twist of blood vessel that is to become our heart, and the last motion of our natural body is our heartbeat. It is there for all of our natural life. And of course there is a beating heart in our spiritual bodies when we come to put them on.
Jehovah
The Lord, in the simplest terms, is love itself expressed as wisdom itself. In philosophic terms, love is the Lord's substance and wisdom is His form. Of course, we feel the Lord's love and hear His wisdom in many different ways, depending on our state in life and how receptive we are. That's why the Lord has so many different names in the Bible, and is referred to in so many different ways.