The oldest known German love song for you both (12th century, tune lost):

Du bist min, ich bin din,
des solt du gewis sin,
du bist beslozzen
in minem herzen,
verlorn ist daz sluzzelin,
du muost och immer darinne sin.

You are mine, I am yours*
you can rely on that
you are locked
in my heart
and the key has been lost
so you have to stay in there forever.

*the ancient legally binding oath for betrothal

Wolfgang