origins
Welsh
From one of the most common Welsh personal names, Rhys, Old Welsh Ris 'ardor'. This was the name of the last ruler of an independent kingdom of Wales, Rhys ap Tewdwr Mawr, who died in 1093 unsuccessfully opposing the Norman advance.
North German and Dutch
Nickname for a very big man, from Middle Low German, Middle Dutch rese ‘giant’.
German
Habitational name from places called Rees or Reese, in Rhineland and Lower Saxony.