This expression has two meanings: one literal (good heart or good hearted), and the other (cheerful or happy heart). The order of the words may be switched, and it is still the same expression and valid in both ways.
The first expression, ‘lev tov’ (in Hebrew on the right), appears in the Bible in Ecclesiastes 9:7. “Go your way, eat your bread with joy, and drink your wine with a merry heart; for God has already accepted your works.”
The biblical verse below uses the same words, but in switched order:
“All the days of the afflicted are evil; but he who is of a merry heart has a continual feast”
An example of the second expression (lev sa•me•ach, in Hebrew on the left):
“A merry heart is a good medicine; but a broken spirit dries the bones”