at a bridge crossing the Fulda river. There are several yet unproven assumptions about the origin of the name. It could be derived from the ancient Castellum Cattorum, a castle of the Chatti, a German tribe that had lived in the area since Roman times. Another assumption is a portmanteau from Frankonian cas, meaning 'valley' or 'recess', and sali meaning 'hall' or 'service building', which can be interpreted as '(town) hall in a valley'.

A deed from 1189 certifies that Cassel had city rights,