My personal favorite: "Hängematte" (hammock) – a hanging mat (something to be hanged + mat)
While actually borrowed from Haitian "hamáka" (it entered German first in the early 15 hundreds as "Hamaco" or "Hamach"), it was soon adopted in the form of a similar sounding native compound. (Also compare the Dutch "hangmat".) Just few native speakers realize, it's not what it reads.