I had never heard or heard of "Du, du liegst mir im Herzen" until coming across it in Lieder, Songs und Gospels 3. This is a North German folksong first noted sometime about 1820. It is a nice, jolly little love song whereby the young man after starting by saying that his beloved is enclosed on his heart goes on to proclaim in every verse that he's the best match for his loved one.
Hard to believe isn't it dear surfer, but I guess times were somewhat different in those days!