The tune is some fifty years older than these lyrics* so it was probably written originally to other lyrics. I can have a look in the middle of next week, but most likely Wilfried or Susanne will have found out until then and posted the response.

* That's a difference between English and German (folk) songs that always amazes me. The English ones are just 'trad.' if they are more than 100 years old, the German ones come with the information (as in the above case) 'text: Paul Gerhardt, 1656, tune: Hans Leo Hasler, 1601'

Wolfgang