I learned German from watching tv nighttime soap operas dubbed into German! Context was so obvious! I remember watching Dallas. Which took place on Souse Fohk, and grown men called their father Deddy.
A friend of mine learned Spanish from two Bibles, one in English and one in Spanish. She had suddenly found herself in Chile with her new Chilean husband, and no way to learn Spanish easily. She made some funny mistakes but speaks fluently now.
The Barbara Cartland books were popular, too. (I never saw what the men read to learn English.)
In many parts of the South of the US, it’s pretty common for people to call their fathers ‘Daddy’ throughout their lives.
I don’t know what ‘Deddy’ might signify in German; but the Germans may have been just trying to copy the phonetics realistically ;-)