[Surname] Re: Is this of Hebrew origin only
If it's Swiss it would seem to be a local variant (with characteristic change from Standard German D to Schwiizertüütsch T)of a topographic name from Northern Germany - Dahl. "Norwegian, Danish, Swedish, North German, and Jewish (Ashkenazic): from any of the medieval and modern forms of Germanic dala-, Old Norse dalr, ‘valley’. Throughout Norway and elsewhere in Scandinavia this is a common farm name. In some cases it is a habitational name from places in Germany named Dahl or Dahle, from the same word. As a Jewish family name this is a habitational name or an ornamental adoption."
Source: Dictionary of American Family Names ©2013, Oxford University Press
Note that in Germany and Denmark it does NOT mean valley. In Denmark it refers to any low-lying area, in Northern Germany it seems to have been borrowed from Low German in the sense of "manor" (presumably from its use in farm names)