From the Irish surname, Gaelic Ó Riain ‘descendant of Rian’. Ryan is associated with the film actor Ryan O'Neal (b. 1941) and is one of several names of Celtic origin that have become very popular throughout the English-speaking world since the 1990s. It is also now well established in North America as a girl's name.
North German: 1. topographic name for a farmer who worked on the heavy clay soil typical of low-lying areas of northern Germany, from Middle Low German klei ‘clay’. 2. habitational name for someone from a place called Klei or Kley (Westphalia, Schleswig-Holstein).