> "Rungholt" probably means "wrong/low wood".

This is an interesting point. Names are often older than they appear.

I have a book on Greek mythology that takes the position that Hercules, including his name, is considerably older than most of the Greek pantheon and should be thought of as a foreign import. But the form of his name ("Heracles") looks so natural in Ancient Greek, "glory of Hera" in the same way that you see other Greeks named Agathocles or Themistocles, that the mythology around the relationship between Hera and Heracles, which is extensive, must have developed from that apparent similarity.

Potentialities like this keep us on our toes when we look at names like "Rungholt".