It could be derived from The traditional Castellum Cattorum, a castle on the Chatti, a German tribe that had lived in the area due to the fact Roman periods. An additional assumption can be a portmanteau from Frankonian cas, indicating "valley or recess", and sali meaning "corridor or assistance making", https://jeffreycgjnq.sunderwiki.com/862324/examine_this_report_on_pflege_zu_hause_kassel