Cognomen ארנאו (Arnau 
, ארנאו 
) , in the entire world, is quite a common family name. The last name ארנאו is habitual in Spain, where it is quite a common surname, Puerto Rico, where it is quite a rare surname, and Argentina. Not in comparison with a country's population, this name is the most popular in Spain, Argentina, and France. Also, ארנאו is the forename as well as the last name.