There is a second derivation of "Esch" as well: Middle High
German "esch" from Old High
German "ezisk" (related to "eat"), originally meaning "corn" but also "(sowed) field" (Saatfeld). It is not clear whether the various
German place-names Esch, Esche or Escher are taken from the tree or the field (the Grimm brothers say in their dictionary, that most of them are from the field).
The ash tree (
German: Esche) hat nothing to do with ashes, whereas the
German surname Escher may well be another word for "Köhler" (with o umlaut) meaning charcoal-burner. So this would be number three.
Andy ;—)